Endocrine Disrupting Chemicals (EDC) may affect mammalian development either indirectly (by affecting implantation, placenta, lactation, etc.) or directly, altering the maturation of target tissues. Studies on reproductive and developmental effects are likely to provide the critical information for risk assessment of most EDC, when proper endpoints are investigated. Toxicity testing guidelines, and especially the two-generation test, are currently being updated with regard to risk assessment of EDC. Particular emphasis is put on selection and validation of the parameters most sensitive to given chemicals and/or mechanisms of action; therefore, a screening battery it is important to address further testing. Under this respect the future use of gene arrays might be a most promising development, when more data will be available. Further points to be considered in a biologically-based assessment of developmental risks include: the identification of critical effects also through the evaluation of dose-response curves; the assessment of the actual exposure and different susceptibility of target tissues; the identification of possible factors of susceptibility and gene-environment interactions; the elaboration of models to estimate the possible additional risk deriving from combined exposures to EDC having similar mechanisms and/or targets.