To investigate the relationship between fever and parasite clearance in falciparum malaria, we studied 54 adults with Plasmodium falciparum infections who were all treated with quinine. The median oral temperature profile showed peaks at 24 h intervals during the first 3 days. Although there was no equivalent pattern evident in the median parasite clearance curve, we hypothesize that small numbers of two distinct parasite broods continued to develop in antiphase through schizogony despite quinine therapy. These data are consistent with previous reports of two dominant broods in untreated humans and monkeys infected with P. falciparum, and highlight the need for an adequate duration of quinine treatment. (C) 2003 Elsevier B.V. All rights reserved.