SummaryIn a series of 60 patients with myelomatosis, 10(17 %) had a hypocholesterolaemia of less than 150 mg/100 ml at the time of diagnosis, always combined with a very high concentration of the M component. 6 of these cases had an IgA and 4 an IgG myeloma.In 5 subjects a pronounced decrease of myeloma immunoglobulin was obtained on melphalan treatment, accompanied in all of them by a normalisation of the cholesterol level ; of the 5 patients without any objective response, 4 conserved the low serum cholesterol.