Quantitative and qualitative analysis of accessory gland proteins in four species of D. immigrans group has been made. Quantitative estimation of these proteins during development of the adult male revealed that there is a gradual increase in the quantity of secretions up to 7 days. The secretions constitute 72, 70, 50 and 54.2% in D.n. nasuta, D.s. neonasuta, D. rubida and D. pararubida respectively. Mating experiments showed that more than 1/3 of this stored secretory protein is transferred into the female reproductive tract during first mating. SDS-PAGE analysis of the accessory gland secretions revealed remarkable simplicity in their patterns, including the absence of age dependent alterations. In all the 4 species analysed, only the low mol. wt. fractions are not glycosylated. It was further observed that the extent of similarity between D.n. nasuta and D.s. neonasuta is greater than between D. rubida and D. pararubida.