In order to provide a scale of genetic distances in the Lagomorpha, biochemical-systematic relationships among Lepus europaeus, Lepus timidus, Oryctolagus cuniculus (Leporidae) and Ochotona rufescens (Ochotonidae) were examined by horizontal starch gel electrophoresis of 38 isozyme systems. Nei's (1978) genetic distances were calculated over 58 presumptive structural loci and used for the construction of numerical dendrograms. The stability of clusters was examined by the jackknife method and by comparison to a Hennigian cladogram. All these procedures revealed a constant picture of lagomorph relationships, which is in accordance with the conclusions drawn from other evidence. Divergence times were estimated using two fundamentally different approaches. They were in good agreement with paleontological data (0.49myr between the Lepus species, 3.65myr between Lepus and Oryctolagus, 37.5myr between Leporidae and Ochotonidae), but only when calculated in different ways at low and at high taxonomic levels. The results suggest a temporal acceleration of the rate of allozyme evolution in the Leporidae due to rapid adaptive radiation of biochemically highly polymorphic taxa.