A Pst-I RFLP polymorphism adjacent to the 3' end of the apolipoprotein A-I gene is reported to associate with hypoalphalipoproteinaemia with dominant inheritance in families identified through accelerated coronary heart disease. This association was not apparent in a large English family identified through voluntary health screening, and with no evident premature coronary disease. Any association could, however, be masked by sex, or by further undetermined variation affecting Pst-I restriction sites. Analysis of this and other polymorphisms present also led to resolution both of disputed paternity and of a long-standing family feud.