The effect of additive administration of methenolone oenanthate (Primobolan) on lipid metabolism was studied in 28 menopausal women with metastasizing carcinoma of the breast. In ten women hyperlipoproteinaemia type IIa was demonstrated in the course of treatment, while in two there was hyperlipoproteinaemia type IIb. One of the latter patients had a myocardial infarction in the course of treatment. There was no relationship between the level of hypercholesterolaemia and the methenolone dosage. Nor was it possible to classify the type of cholesterolaemia as a bile stasis syndrome. The hyperlipoproteinaemia regressed in every case once methenolone treatment was discontinued.