Hypertrophic cardiomyopathy is familial in about 50% of cases and is transmitted in the autosomal dominant mode. The first morbid gene implicated in the disease was the gene coding the beta myosin heavy chain (beta MHC) on chromosome 14. However, only 30% of families have this genetic abnormality. Recently, three new loci have been identified on chromosomes 1q3, 11p13-q13 and 15q2. In order to determine whether other genes could be implicated in the disease a linkage analysis study was performed in a West Indian family. The method is based on the analysis of the distribution of the disease in the family and the microsatellite markers. The microsatellites used were those which recognised the 4 loci previously mentioned and 4 new markers situated and arranged with respect to known microsatellites. The results show that in the family studied, the disease did not concord with the markers of the beta MHC gene or with those recognising the loci on chromosomes 1q3, 11p13-q13 and 15q2. There is, therefore, a fifth gene implicated in familial HCM. The heterogeneity of the disease seems even greater than originally thought.