A study on the prevalence of malaria and the response of Plasmodium falciparum to chloroquine and sulphadoxine-pyrimethamine was conducted in Mvumi area of central Tanzania. Splenomegaly was observed at a rate of 62% and 36% in children and adults respectively. Crude malaria parasite rate was 55.4% in children and 32% in adults. Plasmodium falciparum accounted for the highest proportion (62.7%) of the malaria parasites in the area. This malaria parasite was sensitive to standard dosage of either chloroquine or sulphadoxine-pyrimethamine. Sulphadoxine-pyrimethamine cleared the parasites to undetectable levels by day seven of administration whereas chloroquine cleared parasitaemia in 91% of the subjects by the seventh day. Despite the virtual absence of adult Anopheles mosquitoes during the study period, a larval survey indicated that breeding of Anopheles gambiae s.l. was taking place in nearby irrigation streams. Culex quinquefasciatus was the dominant man-biting mosquito in the area.