Sandfly females, while feeding on the host, excrete urine to concentrate proteins of the bloodmeal and restore weight and water balance. This process, analogous to prediuresis in mosquitoes, was observed in 100% of Phlebotomus papatasi (Scopoli) and 85% of P. duboscqi Neveu-Lemaire females studied. Individual females, however, differed in duration of prediuresis and in the number of ejected urine droplets. In both species the prediuresis generally started 1-2 min after the commencement of feeding and the variation in urine production was positively correlated with the length of feeding. The first one or two droplets were opaque whitish while the remaining ones were clear. Erythrocytes were found sporadically in first droplets of some females. Representative prediuresis in P. duboscqi included 27 droplets, i.e., about 325 nl urine in total, ejected during 8 min of feeding. The study revealed prediuresis in P. papatasi and P. duboscqi as a regular physiological process which may have consequences in transmission of infective diseases.