Ninety-six AML patients in 1st CR were evaluated for peak CD34+ cell levels in peripheral blood (PB) during PBSC mobilization and harvest. Distribution of CD34+ cell peaks was determined and cases were grouped on the basis of 50th and 75th percentile: group A, those having a CD34+ cell peak ≤70 × 10(9)/L (n=48); group B, those having a CD34+ cell peak between 70 and 183 × 10(9)/L (n=24); group C, those having a CD34+ cell peak >183 × 10(9)/L (n=24). Irrespective of post-remission treatment received, group A had a disease free survival (DFS) of 73%, group B a DFS of 51% and group C of 30% (P=0.0003). In intermediate cytogenetic risk patients, those treated by autologous transplantation had a DFS of 68, 33 and 14% in the groups A, B and C, respectively, (P=0.01) whereas after allogeneic transplantation DFS was 87% in group A+B vs 50% in group C (P=0.009). The peak of CD34+ cells in PB, was an independent predictor for DFS in multivariate analysis.