Over a 13-month period, 5,127 adult female mosquitoes were collected on human bait during multiple collecting periods between 1800 and 0600 h in 5 villages in southern Thailand. There were marked differences in the biting activity of different species at each of the villages studied. Anopheles maculatus and Anopheles sawadwongporni were collected most often at dusk or in the first hours of darkness between 1800 and 2100 h. Although specimens of Anopheles dirus were collected consistently between 1900 and 0400 h, peak collections were made between 2000 and 2300 h. Anopheles minimus was collected consistently throughout the night without a clearly discernible peak. Of more than 2,400 Anopheles mosquitoes collected in CDC light traps, 133 specimens (5.4%) contained blood, nearly all of which was identified by enzyme-linked immunosorbent assay (ELISA) to be of bovine origin. Ten specimens contained blood from more than one host species.