All-trans-retinoic acid (ATRA) has a dramatic antitumor effect in patients with acute promyelocytic leukemia (APL). It is hepatically metabolized by cytochrome P-450, and there are known toxicities associated with high levels of this drug. The effects of ATRA can be potentiated by inhibition of cytochrome P-450, which is known to occur with certain drugs. We report a case of a patient with ATRA toxicity thought to be secondary to interaction with fluconazole.