During a 10‐year period (1992–2001) in the region of Southern Denmark, 337 patients aged 15 years or older (range 16–93 years, median 67 years) were diagnosed with acute myeloid leukaemia (AML). Cytogenetic analysis was carried out in 90%, of whom 53% had clonal chromosome aberrations. Some 24% and 31% had only numerical or structural abnormalities respectively. The remaining patients showed both types of abnormalities. Ploidy levels in decreasing order were: pseudodiploidy, 41%; hyperdiploidy, 32%; and hypodiploidy, 27%. Pseudodiploidy characterizes type M3 (70%) and hypodiploidy M6 (56%). Recurrent cytogenetic abnormalities – t(8;21), t(15;17) and inv(16) – were found in 3·3%, 3·3% and 2·0% of all patients respectively. Prognostically intermediate and adverse aberrations were found in 39% and 44%, respectively, of those with an abnormal karyotype. Rare recurrent aberrations were found in two patients in this material. A previously described non‐recurrent abnormality was found to be recurrent in one patient der(20)t(11;20)(q13.2;p13). New, previously undescribed abnormalities were found in 41 patients. Statistically significant correlations were found between t(15;17) and young age (P < 0·001), inv(16) and young age (P < 0·006), −17 and M6 (P = 0·007), and M6 and complex karyotype with five or more unrelated aberrations (P = 0·004). We conclude that this truely population‐based cytogenetic study of adult AML showed distributions of chromosome abnormalities that differ from those described so far.