A new myxosporean, Myxobolus etropli sp. nov., was found to infect the bulbus arteriosus of Etroplus suratensis (Bloch) from brackishwater lagoons of Muttukkadu, Chennai coast, India. A survey from May 1993 to October 1994 revealed a prevalence rate of 33.7% of this parasite. Macroscopic discoloured foci/cysts were seen in the bulbus arteriosus of the fish. The parasite showed strict host and site specificity. Histopathology showed that the infection was restricted to the bulbus. This is the first report of a myxosporean from E. suratensis.