Total of 107 Leiocassis crassilabris caught in Huangzhou along the Yangtze River from May to July, 1999 were examined for infection by Heterosentis parasiluri .The infection rate of the host was 84.1%.The infection rate of the host with body Length 12.0-16.0cm was the highest,while no Heterosentis parasiluri was found in the host with body length above 28.0 cm.The infection intensity of the host was 23.5.There was a negative correlation between body length and infection intensity of the host.r=-0.9043.Parasite population was mainly composed of parasites with length below 3.0 mm.The females were more than the males obviously.Distribution of Heterosentis parasiluri was clumped in the host population.
