Familial hypertrophic cardiomyopathy (FHC) is characterised by autosomal dominant transmission, left ventricular hypertrophy and myocardial disarray. Genetic assessment is of special importance in this disease. Missense mutations of the gene coding for the b-myosin heavy chain (bMHC) have been identified as statistically the most important cause of the disease. Identification of specific mutations may be difficult, thus a simpler method of disease carrier identification is needed. We performed haplotype analysis of six Polish families (47 individuals) with three microsatellite markers located at the bMHC locus. Linkage of the disease locus to the bMHC gene was excluded in 4 out of the 6 families analysed. In 2 families particular haplotypes were coinherited with the disease phenotype. Microsatellite markers allowed identification of 2 carriers of the disease gene in these families among children of the patients.