Estimation of relapse risk in AML after allo-SCT is critical. The negative impact of increased blast count post transplant is widely accepted. Here, we studied cellularity and dysplasia in BM cytomorphology on days 30 and 100 in 112 AML patients who achieved haematological CR after SCT. Overall cellularity on day 30 was normal in 45.3%, reduced in 37.3% and increased in 17.3% of samples (day 100: normal: 54.8%; reduced: 38.7%; and increased: 6.5%). Dysplasia in ⩾10% of cells was frequent on day 30 (granulopoiesis: 25.0% of samples; erythropoiesis: 34.6%; and megakaryopoiesis: 47.7%) and also on day 100. Relapses were less frequent in patients with normal BM cellularity on day 30 (7/34; 20.6%) when compared with reduced (9/28; 32.1%) or increased cellularity (10/13; 76.9%; P=0.001). Estimated 2-year OS was 59.0% for patients with normal overall cellularity, followed by patients with increased (44.0%) and reduced cellularity (31.4%, P=0.009). In contrast, cellularity at day 100 and dysplasia at days 30 and 100 did not correlate with outcome measures. Thus, in the cohort studied, BM cellularity represents a prognostic parameter for the post-transplant period in AML patients. Dysplasia seems to be an unspecific phenomenon in the cohort analysed.