It has been identified that the origin of the heterocyclic amines, a group of suspected human carcinogens is high-temperature heating of proteinaceous materials, e. g., food and plants (tabacco-leaves and woods). The heterocyclic amines have been found in human excretions and rain water. We extracted two of these heterocyclic amines, 3-amino-1-methyl-5H-pyrido[4, 3-b]indole (Trp-P-2) and 3-amino-1, 4-dimethyl-5H-pyrido[4, 3-b]indole (Trp-P-1) in the water of a sewage teatment plant in Japan by HPLC analysis. The concentration of Trp-P-2 and-1 were estimated at about 10^-2μg/L, each. The presence of these compounds shows the possible widespread pollution of surface waters with this class of carcinogens.