We report a case of acquired hypertrichosis lanuginosa associated with rectal cancer and discuss the cutaneous symptoms as a marker of malignancy. A 75-year-old man had noticed increasing growth of hair over his entire body 4 months before he was admitted to our hospital because of bloody stools. Advanced rectal cancer was diagnosed, and he underwent sigmoidocolostomy. After the operation, levels of serum adrenocorticotrophic hormone and cortisone were normal, as were urinary levels of 17-ketosteroids and 17-hydroxycorticosteroids. Levels of carcinoembryonic antigen and carbohydrate antigen 19-9 were slightly elevated. The patient died 5 months after the operation because of peritonitis carcinomatosa. We suggest that hypertrichosis lanuginosa is a marker of internal malignant tumors.