After adjustment for sex and time by Cox's proportional hazards model, the mortality risk of the relatives of carriers of null alleles compared to those with other mutations was 1.05 (95% CI 0.63-1.74, p=0.8). This indicates that allelic heterogeneity is a minor source of variance of mortality from FH. However, we cannot exclude the existance of other mutations of the LDL receptor that are associated with better or worse life expectancy.