Spermatozoa of Sergentomyia minuta Rondani were examined by light, scanning and transmission electron microscopy. The spermatozoon was seen to have a head and a tail. The first was characterized by an acrosomal complex with a thin space containing granular material which was interpreted as a perforatorium. The tail contained a 9+9+0 axoneme and one mitochondrial derivative. These results were compared with the sperm ultrastructure of other Diptera, particularly Psychodidae.