Studies on the composition and distribution of fish species of the Ovwere Stream in the Niger Delta area of Southern Nigeria were conducted between March 1992 and February 1993. A total of 42 species was recorded, of which 29 occurred upstream while 35 and 37 species were represented in the mid and downstream respectively. The mormyrids, characids, cyprinodontids, and cichlids were the most common fish families. The climatic regimes and the flood from the river Ethiope affected the distribution of fishes of some families in the stream. More species were recorded during the rainy season than in the dry one. The different sections showed ichthyofaunal similarity with nearby sections showing higher indices of similarity than the distal ones.