The monthly activity of sand flies, which are vectors of leishmaniasis, was studied from May to October 1997 in three regions (plains, mountainous, coastal) of the Sistan-Bluchistan Province using sticky paper traps. In each village, three houses were selected. 30 sticky traps were installed indoors (bedroom, guestroom, toilet, bathroom) and 30 were installed outdoors (rodent burrows, wall cracks). In total, 8,558 and 1,596 sand fly specimens were collected and identified from outdoors and indoors, respectively. Ten species of Phlebotomus and eight species of Sergentomyia were collected outdoors, and nine species of Phlebotomus and 10 species of Sergentomyia were collected indoors. Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) was the predominant species found indoors in the plains region (58.4% of insects caught in the region) and was active during the whole study period. The P. papatasi peaks of activity were in early May and early October. Sergentomyia clydei (Sinton) was found to be the most abundant species outdoors in the plains region and comprised 64.7% of the total insects caught in the region. Sergentomyia clydei and S. tiberiadis (Alder, Theodor, and Lourie) were the predominant indoor and outdoor, respectively, species from the mountainous region, making up 19.8% and 35%, respectively, of all the insects caught in the region. Phlebotomus sergenti Parrot is a proven vector of urban cutaneous leishmaniasis, and P. alexandri (Sinton) is a probable vector of Kala-Azar, and both were collected during this study. Phlebotomus papatasi was the most predominant species collected indoors in the coastal region (50.8%), its peak activity was in May. Sergentomyia sintoni Pringle was the most predominant species collected outdoors in the coastal region (36.4%), and its peak activity was in October. Awareness of the peak activity times of sand flies can be useful in developing strategies to control the flies.