The three species of large cyprinids living in the streams on the Ruwenzori mountain range, Uganda viz. Barbus somereni, Varicorhinus ruwenzorii and Barhus alluaudi are described. The comparative scarcity of B. alluaudi (about 6 per cent of the population at one site) and the fact that many of its characters are intermediate between those of the other two species suggest that it is a hybrid. Further arguments in favour of this hypothesis are the apparently unbalanced sex ratio in B. alluaudi and the fact that it is most abundant where one of the putative parent species is rare.
The intermediate characters of B. alluaudi are discussed and compared with those of Barbus somereni and Varicorhinus ruwenzorii. The hybrid origin of B. alluaudi cannot be proved but a strong circumstantial case can be constructed for it.