A longitudinal malaria study was undertaken in 1990-91 in 2 adjacent ecological zones in central India: villages in forest and villages away from the forest. The prevalence of Anopheles species varied widely between the 2 ecological settings. In the villages in forest, Anopheles culicifacies and An. fluviatilis were mainly exophilic, whereas in the villages away from forest, An. culicifacies was predominantly endophilic and An. fluviatilis was equally prevalent both indoors and outdoors. The seasonal patterns of malaria transmission were also different between the 2 zones. Plasmodium falciparum was the dominant parasite species in the villages in forest, whereas malaria infection was mainly due to Plasmodium vivax in the villages away from forest. The annual parasite incidence was high in the villages in forest. The failure to control malaria in forested areas is rooted in the terrain and a variety of poorly understood sociological factors.