Exposure of glycosphingolipids to air irreversibly destroys the integrity of these lipids within a few hours. It was established that among the natural constituents of air, ozone, at commonly observed daytime levels, is responsible for the observed degradation. As one product of the reaction of glycosphingolipids with air, an aldehydic fragment containing the carbohydrate moiety was identified. This aldehydic fragment was identical to the one obtained by classical glycosphingolipid ozonolysis. Identical with the latter, the air-induced product is further fragmented by mild alkali treatment with concomitant liberation of the free reducing oligosaccharide. As a consequence of the alteration of glycosphingolipids by air, it was shown that the accuracy of methods of analysis of these glycoconjugates that depend on their physico-chemical integrity, e.g., by tlc-immune overlay, is severely influenced by their prior exposure to the atmosphere.