Diversity and relative abundance of fish species of Rivers Angereb andrnSanja were studied from samples (923 specimens) collected duringrnNovember 2004 to October 2005. The samples were collected in the dryrnseason and wet season. Fish sampling was done using gill nets withrnvarious stretched mesh size, hooks and line, monofilament nets withrndifferent mesh size and cast nets. Ten fish species were identified fromrnthe two rivers and these are included in the families Cyprinidae,rnCichlidae, Mormyridae, Clariidae and Bagridae. The fish speciesrnidentified are East African and Nilo-Sudanic in forms. Cyprinid fish, L.rnforskalii, was the most dominant both in number and weight in bothrnrivers during the two sampling seasons. Analysis of variance shows thatrnthere were significant variations both in number and weight of fishrnspecimens between the two seasons. The three most dominant fishrnspecies in the rivers are L. forskalii, L. cf. intermedius and L. nedgia. Thernlength-weight relationship for these species were found to be curvilinearrnand described by TW = 0.0715TL2.47, TW = 0.0269TL2.96 and TL =rn0.0269TL2.74 respectively in Angereb River. It was TW = 0.01TL3.021, TW =rn0.0057TL3.18 and TW = 0.006TL3.14 for L. forskalii, L. cf. intermedius and L.rnnedgia respectively in Sanja River. The mean FCF for L. forksalii, L.cf.rnintermedius and L. nedgia were 1.26, 1.14 and 1.18 in Angereb River andrn1.09, 1.05 and 1.05 in Sanja River respectively. There was significant variation (ANOVA, P < 0.05) in mean FCF of L. forskalii and L.rnintermedius in the two rivers. In both rivers females were more numerousrn(Chi-square, P < 0.05) than males. The mean absolute fecundity of L.rnforskalii ranging in length from 21 to 25cm FL and mean body weight ofrn229 gm was 48120. The smallest count was 27094 eggs in fish with 14rngm total weight and 22.2 cm fork length. The highest was 120314 eggs inrnfish with 1023 gm total weight and 37 cm fork length. Fecundity of thernspecies in the rivers was linear when related to total weight, fork lengthrnand gonad weight. Key words/phrases: Rivers, Angereb, Sanja, fish diversity, relativernabundance, length-weight relationship, Fulton ConditionrnFactor.