Aquatic snails from south western Zimbabwe belonging to the Bulinus trunscatus/tropicus complex vary widely in shell form suggesting that more than one taxon could be present. This possibility was investigated by making observations on snail samples from 13 populations from the Plumtree area, in respect of allozyme variation (5 polymorphic loci), shell morphology (9 variables), copulatory organ and chromosome number. Comparative data were obtained from snails from north western Zimbabwe identified definitely as B. tropicus. Analysis of the genetic structure revealed a high degree of polymorphism (P) ranging from 0.29-0.80 among populations from Plumtree and expected heterozygosity (H_e) from 0.02-0.22. No enzymatic diagnostic loci were found which could differentiate the different morphs or populations and discriminant function analysis on the morphological data showed an overlap of morphs among populations. Snails analyzed for chromosome number were all diploid (2n = 36). Snails exposed to Schistosoma haematobium mira-cidia were all refractory. This information supports the view of a single species, B. tropicus, which is differentiated due to migration barriers and where environmental variables might be implicated in the morphometric divergence.