Camptodactyly (MIM 114200) is a digit deformity characterised by permanent flexion contracture of fifth fingers at the proximal interphalangeal (PIP) joints. The sporadic cases are common but a familial occurrence is not much appreciated. In an attempt to identify the genetic basis of camptodactyly, we have analysed a large German family with camptodactyly segregating in an autosomal dominant fashion. The affected family members exhibited clinical features of fifth finger camptodactyly and knuckle pads on the crooked fifth finger and on fingers 2-3. Typically, women were more severely affected than men. Microsatellite analyses of five candidate loci known to be associated with camptodactyly-like phenotypes did not show co-segregation with the phenotype in our family. A genome-wide linkage scan using a total of 414 microsatellite markers gave significant evidence of linkage between the familial phenotype and chromosomal locus 3q11.2-q13.12 (maximum two-point LOD score 3.04). The key recombination events showed that the phenotype localises between markers D3S2465 and D3S3044, spanning an interval of approximately 15 cM. This study reports the first genetic locus linked to isolated autosomal dominant fifth finger camptodactyly with knuckle pads and proves the hypothesis that camptodactyly is distinct from camptodactyly-associated phenotypes including Dupuytren contracture. Additional studies of other families will be necessary to determine the existence of genetic homogeneity or heterogeneity of the anomaly and to narrow down the genetic interval to identify the responsible gene. Since genetic heterogeneity for isolated camptodactyly is likely, we propose to designate the 3q11.2-q13.12 locus as CAMPD1 (ie, camptodactyly 1).