We studied platelet engraftment in 58 patients with acute myeloid leukemia in first remission treated with autologous stem cell transplantation (ASCT) to determine whether CD34+ cell doses >10 x 10(6)/kg were associated with faster platelet engraftment. We compared engraftment rates in patients receiving CD34+ doses between 5 and 10 x 10(6)/kg (standard-dose ASCT) with those receiving doses > or =10 x 10(6)/kg (high-dose [HD] ASCT). We also studied neutrophil engraftment rates and platelet and red blood cell transfusion requirements. In multivariate adjusted models, the rate of platelet recovery to > or =20,000/microL was 4-fold greater among subjects who received HD-ASCT (hazard ratio [HR], 4.1; confidence interval [CI], 1.8-9.2; P =.001), with median recovery times of 14 versus 28 days. The rate of platelet recovery to > or =50,000/microL was 2-fold greater (HR, 2.1; CI, 1.3-5.9; P =.01), with median recovery times of 19 versus 46 days. Faster platelet recovery resulted in the need for fewer platelet transfusions among the subjects who received HD-ASCT (mean transfusions, 3.7 versus 9.8; P =.005). Although not statistically significant, neutrophil recovery data in the adjusted model suggested a similar effect in the HD-ASCT group, with faster engraftment times at absolute neutrophil counts >500/microL (median, 9.2 versus 12 days; HR, 1.6; CI, 0.69-3.5; P =.29) and absolute neutrophil counts >1000/microL (median, 9.5 versus 12 days; HR, 1.3; CI, 0.56-2.8; P =.58). Subjects who received HD-ASCT required fewer red blood cell transfusions (4.0 versus 9.8 units; P =.01). Our findings suggest that CD34+ cell doses >10 x 10(6)/kg CD34+ result in faster engraftment and fewer red blood cell and platelet transfusions.