A simple test for determining the teratogenic potential of compounds is described using embryonic limb bud cells in culture. These mesenchyme cells multiply and differentiate into chondrocytes during a 6-day culture period. The extent of chondrogenesis is assessed by staining for the cartilage specific proteoglycan with alcian blue. The amount of stain is then measured spectrophotometrically. Compounds which interfere with growth or differentiation reduce the amount of proteoglycan and as a consequence, reduce alcian blue staining. Compounds can be added directly to the media or be activated using several different metabolizing systems. The dose of a compound needed to reduce alcian blue staining by 50% is designated the teratogenic potential (TP50) of that compound. TP50's of proven teratogens compare favorably with in vivo teratogenic doses of the teratogens.