Morphine was detected by immunohistochemistry on sections of third stage larvae of Calliphora vomitoria (Diptera, Calliphoridae) reared on minced beef previously treated with morphine hydrochloride. Detection was accomplished by means of an avidin-biotin-peroxidase-complex method. Positive specimens showed specific staining of the haemolymph and a more intense immunoreaction in an area at the limit between exocuticle and endocuticle. These results were evidence of morphine accumulation inside the cuticle of Diptera larvae during their development. During the pupariation, the larval cuticle was transformed into the sclerotized puparium. This study claimed to contribute to the research into metabolism of drugs in fly larvae using immunochemical techniques. It confirmed previous studies that detected drugs in empty puparia using techniques employed in hair extractions. It further served to focus attention on the significance of empty puparia in cases where normal toxicological specimens or living necrophagous insects were not present. Figures, references