Low density lipoprotein in Ehrlich tumor bearing mice was studied on the cholesterol conversion to steroid hormone in serum and liver, and which were compared with those of normal mice by means of thin-layer chromatography and radioactivity. (3)H-cholesteryl ester was completely formed by 6 hours after the (3)H-cholesterol administration from peritoneal cavity. The most part of the cholesterol was esterified and incorporated into lipoproteins. The metabolic processes were studied in Ehrlich ascites carcinoma bearing mice. The cholesterol conversion to steroid hormone in tumor bearing mice L D L was elevated twice to four times than the normal.