The OECD Test Guidelines are recognised internationally as the standards for non-clinical environment and health safety testing of chemicals and chemical products. They are an integral part of the Council Decision on the Mutual Acceptance of Data and are used to support chemical safety regulations in many countries. Each Test Guideline provides sufficient detail for chemicals to be tested in the same manner in laboratories around the world.

These Guidelines are continuously expanded and updated to reflect advances in scientific knowledge and techniques and to meet the regulatory needs of member countries. They are developed with the assistance of experts from regulatory agencies, academia, industry and environmental and animal welfare organisations.

The OECD Guidelines for the Testing of Chemicals are split into five sections:

• Section 1: Physical Chemical Properties
• Section 2: Effects on Biotic Systems 
• Section 3: Environmental Fate and Behaviour 
• Section 4: Health Effects  
• Section 5: Other Test Guidelines

The OECD Series on Testing and Assessment includes materials related to the testing and assessment of chemicals. Some of these publications support the development of OECD Test Guidelines, such as validation reports, guidance documents and detailed review papers.

56 new, updated and corrected Test Guidelines (in English and French) were published on 25 June 2025. These guidelines ensure that testing keeps pace with scientific progress and promote best practices in chemical testing, in line with the Replacement, Reduction and Refinement of animal experimentation (3Rs) Principles, and that data generated are covered by Mutual Acceptance across member and adhering countries.

One new Test Guideline:

• Test No. 254: Mason bees (Osmia sp.), Acute Contact Toxicity Test

The following Test Guidelines were updated to allow collection of tissue samples for omics analysis:

• Test No. 203: Fish, Acute Toxicity Test 
• Test No. 210: Fish, Early-life Stage Toxicity Test
• Test No. 236: Fish Embryo Acute Toxicity (FET) Test
• Test No. 407: Repeated Dose 28-day Oral Toxicity Study in Rodents
• Test No. 408: Repeated Dose 90-Day Oral Toxicity Study in Rodents
• Test No. 421: Reproduction/Developmental Toxicity Screening Test
• Test No. 422: Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test

The following Test Guideline was updated to include a new Defined Approach for surfactant chemicals:

• Test No. 467: Defined Approaches for Serious Eye Damage and Eye Irritation

The following Test Guideline was updated to introduce a variation in the STE method, the STE 0.5, used in the Test No. 467 Defined Approach for surfactant chemicals:

• Test No. 491: Short Time Exposure In Vitro Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage

The following Test Guideline was updated to allow in vitro and in chemico methods in TG 442C, TG 442D and TG 442E to be used as alternate sources of information, and to include a new Defined Approach for the determination of point of departure for skin sensitization potential:

• Test No. 497: Defined Approaches on Skin Sensitisation

The following Test Guideline was updated to clarify analytical requirements, calculations and statistical analyses:  

• Test No. 239: Water-Sediment Myriophyllum Spicatum Toxicity Test

The following Test Guidelines were updated to remove the EpiSkin TM model which is no longer commercially available:

• Test No. 431: In vitro skin corrosion: reconstructed human epidermis (RHE) test method
• Test No. 439: In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method

The following Test Guideline was updated with a variant of the IL-2 Luc assay, the IL-2Luc LTT assay:

• Test No. 444A: In Vitro Immunotoxicity IL-2 Luc and Il-2 Luc LTT Assays

The following Test Guideline was updated for additional guidance on the utility of eye histopathology:

• Test No. 437: Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage

The following Test Guideline was updated to introduce a sub-categorisation criterion for skin senstisers for the ELISA_BrDU method:

• Test No. 442B: Skin Sensitization: Local Lymph Node Assay: BrdU-ELISA or –FCM

This Test Guideline was updated to provide more clarity to the endocrine disrupter-related endpoints and the developmental immunotoxicity measurements:

• Test No. 443: Extended One-Generation Reproductive Toxicity Study

The following Test Guideline Test Guideline was updated to include borderline ranges:

• Test No. 442C: In Chemico Skin Sensitisation: Assays addressing the Adverse Outcome Pathway key event on covalent binding to proteins

The following Test Guideline was updated to  ensure that the results specified for the recommended proficiency chemicals all align with the expected outcomes using the new data interpretation procedure agreed in 2022:

• Test No. 456: H295R Steroidogenesis Assay

The following Test Guidelines were updated to clarify the use of historical control data in the interpretation of results:

• Test No. 470: Mammalian Erythrocyte Pig-a Gene Mutation Assay
• Test No. 488: Transgenic Rodent Somatic and Germ Cell Gene Mutation Assays

The following Test Guideline was updated based on experience gained in its application:

• Test No. 506: Stability of Pesticide Residues in Stored Commodities

The following Test Guidelines were corrected for radioactive labelling position:

• Test No. 111: Hydrolysis as a Function of pH
• Test No. 307: Aerobic and Anaerobic Transformation in Soil
• Test No. 308: Aerobic and Anaerobic Transformation in Aquatic Sediment Systems
• Test No. 316: Phototransformation of Chemicals in Water – Direct Photolysis

The following Test Guideline was corrected:

• Test No. 492: Reconstructed human Cornea-like Epithelium (RhCE) test method for identifying chemicals not requiring classification and labelling for eye irritation or serious eye damage

The OECD Test Guidelines are widely acknowledged as the global standard for chemical testing and are used by governments, industry and independent laboratories for regulatory purposes. Regularly updated to reflect scientific advancements and evolving regulatory requirements, the guidelines are essential for chemical notification and registration.

This brochure provides a comprehensive overview of how these guidelines are developed, refined and published. It also outlines the collaborative processes that maintain their global relevance and ensure their reliability.

This presentation introduces a practical checklist to guide developers preparing to submit an in vitro method for OECD Test Guideline (TG) development. The checklist aims to help method developers anticipate challenges, engage with relevant stakeholders early and ensure their methods are ready for regulatory use.