Specimens of the two nominal species Haliplus sibiricus Motschulsky, and H. wehnckei Gerhardt, were examined by enzyme electrophoresis and morphometrical methods. Beetles collected from five different localities along the north Swedish coast were screened at ten different loci, and paramere shape variation was studied using Elliptic Fourier description. Wright's F-statistics were computed to assess population structure, and PLS-analysis (Projections to Latent Structures modelling) to estimate shape differences. We revise the distribution of the two species in Sweden. The results show a gross overlap and sympatry. Paramere shape analyses indicate the existence of two different forms, which change in frequency with latitude. There are morphologically intermediate specimens that would be difficult to place into either species. Genetic data do not support the nominal species status, and FST-values indicate moderate genetical differences between the populations. We propose that H. sibiricus and H. wehnckei are conspecific. They are either subspecies, or represents two different morphotypes of a clinally varying character. Our data support the latter. Accordingly, H. wehnckei Gerhardt, 1877, is a junior synonym of H. sibiricus Motschulsky, 1860, syn. n.