Between 1971 and 1984, 22 of 190 adult patients (11.6 per cent) with acute leukemia seen at the University of Arizona had hypocellular acute leukemia (HAL), defined as lymphoblasts or myeloblasts (plus atypical promyelocytes) of greater than or equal to 30 per cent, but marrow cellularity of the core biopsy or clot section of less than or equal to 50 per cent based on a 1000 point count. These 22 patients with HAL plus the 48 previously published patients with well documented HAL (combined series of 70 patients) were evaluated in detail with multivariate analysis. The median leukocyte count was 2700/microL, hemoglobin of 8.2 g/dl, and platelet count 63,000/microL. Circulating blasts were noted in 27 of 52 patients (52 per cent). Twenty-seven of 34 patients (79 per cent) had abnormal cytogenetics. The overall median survival was 8 months (range: 0.1-48). The median survival for the 22 patients managed with supportive care alone was 4 months, 6 months for the 16 patients treated with non-aggressive induction therapy, and 13 months for the 32 patients treated with aggressive induction therapy (p less than 0.02 versus other categories). Multivariate analysis confirmed that aggressive induction therapy was a major favourable prognostic factor (p = 0.016). Multivariate analysis of the aggressively induced patients revealed that younger patients (less than or equal to 65; p = 0.04) and patients with no AHD (p = 0.09) lived longer. Thus, aggressive remission induction can be attempted in HAL and appears to contribute to prolonged survival especially under age 65 years.