Forty five year old male suffering from relapsed acute promyelocytic leukemia (APL) was treated with all-trans retinoic acid (ATRA) and attained second complete remission (CR) without bone marrow hypoplasia. He was diagnosed as having APL in September 1989. The DCMP-85 regimen first induced CR in October, however the disease relapsed in September 1990. The DCMP-85 and and the MEC (MIT, ETOP, Ara-C) regimens were applied for re-induction without success. Then, 45 mg/m2/day ATRA was given orally from December 28, 1990. Laboratory data before ATRA treatment were as follows; 35.4% leukemic cells in the bone marrow, Hb 11.0 g/dl, Plt 130,000/microliters, WBC 5,100/microliters without leukemic cells, and no DIC was detected. During the treatment, his bone marrow was examined frequently. The bone marrow series showed no hypoplasia at any time and gradual reduction of leukemic cells with proliferation of mature granulocytes. CR was attained on January 21, 1991. DIC did not develop. Cytogenetic anomalies including t(14;17;15) (q24;q11.2;q22) reduced from 29/30 cells at relapse to 4/30 cells at the time of CR. Dryness of mouth and lips, irritation around eyes and the elevations of GOT, GPT and triglyceride level were seen as the side effects of ATRA, however they were tolerable.