Anopheline vectors and malaria transmission were studied in 2 river-irrigated, rice-growing districts of eastern Afghanistan from May 1995 to December 1996. Clinical malaria was monitored in 12 rural villages (population 14,538) by passive case detection at local clinics. Adult mosquitoes were collected by space-spraying of living quarters and stables and by cattle bait catches. Mosquito head-thoraces (17,255 specimens) were tested for Plasmodium falciparum and P. vivax circumsporozoite protein (CSP) using enzyme-linked immunosorbent assay. The recorded incidence of P. vivax and P. falciparum was 199 and 41 episodes per 1000 person years, respectively. Twelve species of anopheline were recorded; Anopheles stephensi comprised 82% and A. culicifacies 5%. Eight species tested positive for CSP: A. stephensi, A. culicifacies, A. fluviatilus, A. annularis, A. pulcherrimus, A. maculatus, A. splendidus and A. superpictus. Among infected mosquitoes 46% were positive for P. falciparum, 45% for P. vivax VK-247, and 9% for P. vivax PV-210. Estimates of the feeding rates of infective vectors on humans indicated that A. stephensi would contribute 76% of infective bites, A. fluviatilis and A. pulcherrimus 7% each, and A. culicifacies and A. superpictus 3% each. The overall infective vector feeding rate correlated with the P. vivax incidence rate in the human population. The conventional view of A. culicifacies being the main rural vector and A. stephensi important only in urban settings needs to be reconsidered in western outreaches of the Indo-Pakistan subcontinent.