Three carcinogenic heterocyclic aromatic amines, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhlP), and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMelQx), have been detected by capillary zone electrophoresis in rain water and accompanying suspended particulates collected during haze episodes originating from major forest fires in Southeast Asia. The haze enveloped much of Southeast Asia, including Singapore, during August through October 1994. These compounds were not detected in rain samples collected in November 1994 after the haze had dissipated. This finding suggests that combustion of wood and vegetation is a likely source of these carcinogens in rain water.