The evaluation of behavioral teratogenic effects in animal studies is discussed in light of the results of the Collaborative Behavioral Teratology Study (CBTS) and the U.S. EPA's guidelines for the risk assessment of suspect developmental toxicants. Although behavioral teratology testing is not routinely required by the U.S. regulatory agencies, data on existing chemicals are reviewed and evaluated in the risk assessment process. Recent efforts in methods development and validation, including the CBTS, have provided guidance for the development of regulatory testing requirements in specific cases. For example, the U.S. EPA has recently published a proposed test rule which includes developmental neurotoxicity testing for the triethylene glycol ethers. Generic guidelines for such testing may be developed which can then be applied on a case-by-case basis.