Electrophoretic analysis of the five species in the genus Uma reveals three distinct groups. U. exsul and U. paraphygas, the two Mexican species, are genetically divergent from one another and from the three Californian species, U. notata, U. inornata and U. scoparia, which cluster closely. The genetic distance between U. exsul and U. paraphygas (D = 0.25) is comparable to between-species distances for other lizards; the U. notata-U. inornata-U. scoparia group exhibits genetic distances (D = 0.02) similar to those between conspecific populations of other taxa. I consider the U. notata-U. inornata-U. scoparia group a single species. Heterozygosity levels are extremely low in Uma (1%) and are comparable to those of recently studied non-vagile fossorial species such as Bipes and Anniella.