It has been shown using ELISA and affinity chromatography, that extracts from heat-shocked Drosophila melanogaster larvae and cultured cells react with monoclonal antibodies raised against bovine a-crystallin. It is suggested that this cross-reactivity is associated with the region of the sequence corresponding to residues 98–108 of the bovine otA-crystall in chain. This region may be important for the functions of both a-crystallin and the heat-shock proteins.