The chemical composition of epicuticular wax from cabbage plants grown in vitro was compared with that from plants grown in a greenhouse. There was a greater percentage of polar compounds (fatty acids, primary alcohols, aldehydes, and esters) and less alkanes and secondary alcohols in wax from cultured plants relative to those from greenhouse plants. Homologues in each class were more evenly distributed and had a greater range of chain lengths in wax from cultured plants. The high proportion of polar components in wax from cultured plants might be a factor in water loss when the plants are transferred to the greenhouse. Possible explanations for the altered wax composition in plants grown in vitro include increased relative humidity and decreased light intensity characteristic of in vitro conditions.