Three species in the group of "small" Barbus from West Africa were analyzed by enzyme electrophoresis to assess their genetic differentiation. Comparison with a species of "large" Barbus from the same region showed that the "small" Barbus are certainly diploid and the "large" tetraploid. They clearly form two distinct lineages. Phenetic dendrograms (Nei distances) and cladograms (compatibility networks) of the genus Barbus are proposed, based on three African diploid species, two diploid species from Saudi Arabia and Southeast Asia, one African tetraploid species, and two French tetraploid species. These trees reveal two sets of species, i.e. diploid and tetraploid. Several methods of data processing are suggested for overcoming the difficulties involved in simultaneously analyzing species with different ploidy levels.