The potential usefulness of the retinoids, a large group of synthetic compounds chemically and structurally related to vitamin A, in the treatment of severe dermatologic diseases and in the prophylaxis and therapy against cancer is severely limited because of their potential teratogenicity. CASE analysis of published retinoid data from the hamster teratogenicity assay and the limb bud "spot" culture system has targeted the hydrophobic region of the retinoids as having the greatest effect on the range of potencies studied. In addition, log p's (as calculated by the CASE program) below a certain value appear to unilaterally result in nonteratogenic retinoids in the in vivo hamster assay system.