Background: Little is known about the causes of adult leukemia. A few small studies have reported a reduced risk associated with regular use of nonsteroidal anti-inflammatory drugs (NSAID). Methods: In a population-based case-control study, we evaluated analgesic use among 670 newly diagnosed myeloid leukemia cases [including 420 acute myeloid leukemias (AML) and 186 chronic myeloid leukemias (CML)] and 701 controls aged 20 to 79 years. Prior use of aspirin, ibuprofen, acetaminophen, other NSAIDs, and COX-2 inhibitors was assessed and included frequency, duration, and quantity. ORs and 95% CIs were calculated using unconditional logistic regression adjusting for potential confounders. Results: Regular/extra strength aspirin use was inversely associated with myeloid leukemia in women (OR = 0.59, 95% CI = 0.37-0.93) but not in men (OR = 0.85, 95% CI = 0.58-1.24). In contrast, acetaminophen use was associated with an increased risk of myeloid leukemia in women only (OR = 1.60, 95% CI = 1.04-2.47). These relationships were stronger with increasing dose and duration. When stratified by leukemia type, aspirin use was inversely associated with AML and CML in women. No significant overall associations were found with ibuprofen or COX-2 inhibitors for either sex; however, a decreased risk was observed with other anti-inflammatory analgesic use for women with AML or CML (OR = 0.47, 95% CI = 0.22-0.99; OR = 0.31, 95% CI = 0.10-0.92, respectively). Conclusions: Our results provide additional support for the chemopreventive benefits of NSAIDs, at least in women. Because leukemia ranks fifth in person-years of life lost due to malignancy, further investigation is warranted. Impact: NSAIDs may reduce, whereas acetaminophen may increase, myeloid leukemia risk in women.