According to currently available information, the metacercaria of one heterophyid trematode, Haplorchis, is commonly found in freshwater fishes, especially the cyprinoid group. Thus, in an investigation into the level of Haplorchis metacercaria infection in cyprinoid fishes, comprising ten species, 811 cyprinoid fishes were captured from canals, reservoirs and rivers in 6 districts of Chiang Mai Province and 4 districts of Lumphun Province, Thailand, 43.03% of the fishes comprising seven species viz Puntius leiacanthus, P. gonionotus, P. orphoides, P. stolickkae, Cirrhina spp, Rasbora spp and R. lateristriata, were found infected, with the prevalence of infection at 77.29, 70.31, 56.52, 47.14, 18.48, 7.94 and 5.18% respectively. Infected fishes were collected from Mae Rim and Sansai districts of Chiang Mai, and Pasang, Ban Hong and Li districts of Lumphun. It should be noted that the Haplorchis metacercariae are commonly found along with Haplorchoides metacercariae. Both minute heterophyids metacercariae were mainly localized in scales, a few were found in fins and gills of fishes.