Allelic frequencies of polymorphic variants at the lipoprotein lipase gene locus have been measured in subjects with premature coronary artery disease and dyslipidaemia. One of the polymorphic variants involves a termination codon in exon 9 that produces a truncated protein whose Michaelis constants for triolein or chylomicra are identical to the native enzyme but whose Vmax for both substrates may be increased. The other informative polymorphism is a HindIII site in intron 8 that shows marked assymetric allelic distribution in subjects with hypertriglyceridaemia/low HDL syndrome and in subjects with premature coronary artery disease. It is hoped that the marker may lead to the identification of an aetiological mutation in its vicinity to account for these disease associations.