A 54-year-old man was referred to our hospital because of petechiae and pancytopenia. Bone marrow aspiration showed a normocellular marrow with 92.4% promyelocytes. PML/RAR alpha mRNA was detected by reverse transcription polymerase chain reaction. On the basis of above data, a diagnosis of acute promyelocytic leukemia (APL) was made, and treatment with all-trans retinoic acid (ATRA) at a dose of 60 mg/day was begun. Fourteen days after the start of treatment, the patient developed paralytic ileus, accompanied by hyperleukocytosis, high fever, renal dysfunction and elevation of the serum FDP level. There was no evidence of infection. At this time, retinoic acid syndrome was suspected, and therefore steroid pulse therapy was started, which led to an improvement of the symptoms within four days. This case suggests that ATRA may have an adverse effect on the small intestine, causing paralytic ileus.