Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder with genetic heterogeneity. Up to three loci are involved in this disease, PKD1 on chromosome 16p13.3, PKD2 on 4q21, and a third locus of unknown location. Here we report the existence of locus heterogeneity for this disease in the Argentinian population by performing linkage analysis on 12 families of Caucasian origin. Eleven families showed linkage to PKD 1 and one family showed linkage to PKD2. Two recombinants in the latter family placed the locus PKD2 proximal to D4S1563, in agreement with data recently published on the cloning of this gene. Analysis of clinical data suggests a milder ADPKD phenotype for the PKD2 family.