The prognostic significance of in vitro growth characteristics of leukemic blast cells in acute myeloid leukemia (AML) is well established in the literature. This review focuses on semi-solid colony growth from bone marrow mononuclear cells (BMMCs) of 322 newly diagnosed patients with AML in relation to the three established cytogenetic risk groups. The median numbers of colonies derived from cytokine-stimulated BMMCs significantly differed between patients with favorable karyotypes (2/10(6)), intermediate cytogenetics (12/10(6)) and unfavorable abnormalities (51.5/10(6)). Colony growth in the absence of stimulatory cytokines was assessed in 113 patients. Individuals with unfavorable karyotypes exhibited significantly more often partial or full autonomous growth in vitro when compared to the intermediate and favorable prognostic group. Median stimulated colony growth of patients who entered complete remission (CR) was 9/10(6) BMMCs compared with 63 in patients with no response. Both, cytokine-stimulated as well as autonomous colony formation, significantly discriminated between patients regarding survival. However, multiple regression analysis revealed cytogenetic risk groups as the most important predictor for achieving CR, with colony growth adding no additional prognostic information. In conclusion, semi-solid colony growth predicts response to treatment and survival in AML but is clearly related to karyotypic abnormalities.