Abstract: Tetrahymena pyriformis and Epistylis sp. found on the body surface, mouth and oesophagus of freshwater leech, Nephelopsis obscura were studied. Tetrahymena pyriformis was defined on the body surface, in the mouth and oesophagus of Nephelopsis obscura. But Epistylis sp. was only determined on the body surface of leech. The mean length of Tetrahymena pyriformis was 42±3.5 μ (X±SD, range 39-44 μ , n=30) with a mean width of 26±4.9 μ (X±SD, range 22-29 μ , n=30). Epistylis sp. length was 48±3.8 μ (X±SD, range 45-52 μ , n=30) a width of 38±2.9 μ (X±SD, range 36-42 μ , n=30).