158 Seattle pedigrees selected through hyperlipidemic survivors of myocardial infarction were partitioned into nuclear families with pointers, and complex segregation analysis under a mixed model (major locus and multifactorial transmissible component) was performed on cholesterol and triglyceride measurements. Results confirm the existence of a dominant allele for hypercholesterolemia, whereas for triglyceride segregation of a major locus was not supported. Familial combined hyperlipidemia may be an artefact of multi-trait two-stage selection.