Hypertension, a major risk factor for cardiovascular diseases, is thought to be inherited to some extent. However, the nature of its genetic component remains unresolved. In the present study, data from a single large kindred (the HGAR1 pedigree) were used to search for evidence of single gene and multifactorial effects on diastolic blood pressure. Commingling analyses found that a mixture of three distributions fit the data significantly better than a single normal distribution, suggesting a major effect influencing diastolic blood pressure levels. However, segregation analysis, using regressive models, indicated that the transmission probabilities were not consistent with Mendelian expectations. There was no evidence of either major gene or polygenic effects on diastolic blood pressure levels in this family.