Overproduction of VLDL (very-low-density lipoprotein) particles is an important cause of FCHL (familial combined hyperlipidaemia). It has been shown recently that VLDL production is driven by the amount of hepatic fat. The present study was conducted to determine the prevalence of fatty liver in relation to the different fat compartments and lipid parameters in FCHL. A total of 68 FCHL patients, 110 normolipidaemic relatives and 66 spouses underwent ultrasound of the abdominal region to estimate the amount of subcutaneous, visceral and hepatic fat. Skinfold callipers were used to measure subcutaneous fat of the biceps, triceps, subscapular and supra-iliacal regions. Fatty liver was observed in 18% of the spouses, 25% of the normolipidaemic relatives and 49% of the FCHL patients. After adjustment for age, gender and body mass index, the prevalence of fatty liver was significantly higher in FCHL patients compared with spouses [OR (odds ratio), 3.1; P=0.03], and also in the normolipidaemic relatives compared with spouses (OR, 4.0; P=0.02), whereas no differences were observed between FCHL patients and normolipidaemic relatives (OR, 0.8; P=0.58). In the normolipidaemic relatives and FCHL patients combined, both visceral fat mass and subcutaneous abdominal fat were independent predictors of fatty liver (P<0.001 for both fat compartments; FCHL status corrected). Of interest, fatty liver stages were correlated with both VLDL-apoB (apolipoprotein B) and VLDL-triacylglycerols (triglycerides) in a representative subset (n=69) of patients and relatives (r(2)=0.12, P=0.006; and r(2)=0.18, P=0.001 respectively). These results show that fatty liver is a central aspect of FCHL, i.e. patients and normolipidaemic relatives. Both visceral and subcutaneous adiposity contribute to its 3-4-fold higher risk in FCHL.