Plasma lipid parameters (triglycerides, total cholesterol and high density lipoprotein cholesterol) were measured in 7 children with juvenile chronic granulocytic leukaemia, of whom 3 were with and 4 without xanthomas. In all cases, whatever the stage of the disease, these parameters were extremely altered. Plasma triglycerides were generally increased, total and HDL cholesterols were very low. No relationship seems to exist between these values and the occurrence of xanthomas.