The polytypic carabid Carabus punctatoauratus, which inhabits the northern chains of the middle and eastern Pyrenees, was investigated with respect to allozyme polymorphisms. Twenty-nine local populations distributed over nearly the entire range of the species were studied. Out of 18 enzymes tested, four were found to be polymorphic: aspartate aminotransferase-1 (AAT-1), an esterase (EST-X), glucose-6-phosphate isomerase (GPI) and 6-phosphogluconate dehydrogenase (6-PGD). The total number of allozymes detected was 7 for AAT-1, 14 for EST-X, 13 for GPI and 7 for 6-PGD; in local populations, the sum of the number of allozymes varied from 7 to 24. With a few exceptions, the genotype frequencies of the local populations were in Hardy-Weinberg equilibrium. In two loci (Est-x and Gpi) an allele frequency gradient along the WNW-ESE axis of the range was detected. Moreover, several alleles with a discontinuous spatial change of frequency were found. The peripheral populations studied (from the Massif du Canigou in the east and from the Massif du Midi de Bigorre in the west) were substantially differentiated. On the other hand, populations distributed over the large central region of the species exhibited similar sets of allozymes. Thus, in the central region, a congruence in the degree of morphological and biochemical differentiation has not been found. However, in several cases, local populations obviously belonging to the same metapopulation showed significant differentiations, which seem to be caused by genetic drift. It is concluded that, in Carabus punctatoauratus, allozyme differentiations among local populations are usually transient phenomena, which are levelled again by metapopulation dynamics ('drift levelling').