Metacercaria from freshwater fishes of Mae Sa stream, Doi Suthep-Pui National Park. Chiang Mai Province were investigated between January 1997-December 1998, 3,133 fishes of 32 species were collected. The prevalence of infection of fishes was 19.087% (598/3, 133). Six genera of metacercaria were recovered as follows: Acanthostomum sp, Centrocestus caninus, Haplorchis taichui, Haplorchoides sp, Posthodiplostomum sp and Stellantchasmus falcatus. The prevalence of each species of metacercaria was observed from total number of fishes as follow: 1.149% (36/3,133), 3.753% (96/3,133), 1.883% (59/3,133), 9.735% (305/3,133), 0.096% (3/ 3,133) and 2.553% (80/3,133) respectively. The highest prevalence of parasites were observed: Acanthostomum sp was 11.111% from Trichopsis vittatus; Centrocestus caninus was 100% from Xenentodon cancila; Haplorchis taichui was 12.108% from Mystacoleucus marginatus; Haplorchoides sp was 55.532% from Mystacoleucus marginatus; Posthodiplostomum sp was 1.176% from Dermogenus pusillus; Stellanchasmus falcatus was 100% from Xenentodon cancila. Centrocestus caninus, Haplorchis taichui and Stellantchasmus falcatus have been reported from human and mammals. The rest were reported from birds, fishes and reptiles.