Gamete competition models were used to explore the relationships between 13 ACE gene polymorphisms and plasma ACE concentration in a set of Nigerian families. Several markers in the 5 and 3 regions of the gene were significantly associated with ACE concentration (P < 10 UTR and the 3 region of the gene were also analysed; in addition to G2350A, in the 3 region, two markers from the 5 UTR (A-5466C and A-240T) were found to be associated with ACE concentration. These results are consistent with reports that have suggested the presence of at least two ACE-linked QTLs, and demonstrate the utility of gamete competition models in the exploratory investigation of the relationship between a quantitative trait and multiple variants in a small genomic region.....