Nature of infestation of Saurida tumbil by the adult cestodes Penetrocephalus ganapatii and Bothriocephalus indicus is presented. A detailed study of P. ganapatii infection has been carried out and the results regarding histopathological studies, incidence and intensity of infection, effect of infection on body weight, liver weight, hepato-somatic index, peripheral blood and proximate composition of liver and white muscle are presented. The incidence and intensity of infection very significantly with season and with growth of the fish. Histopathological changes indicate that the infected fish become anaemic. The anaemia is of the macrocytic type. Infection causes depletion of the basic energy reserves in the liver and white muscle of the fish. Since B. indicus exclusively occurs in fish infected with P. ganapatii and since the intensity of infection in very low, the actual damage caused by this worm is not clearly understood.