Bone mineral density (BMD) of the lumbar spine was measured in 97 long‐term survivors of childhood cancer 5–23 years after diagnosis using dual‐energy X‐ray absorptiometry (DXA). They had been treated for acute leukemia (n = 22), brain tumors (n = 16), lymphomas (n = 16), Wilms' tumor (n = 10), neuroblastoma (n = 7) and other cancers (n = 26). The correlations between BMD and the Z‐scores for weight for height, height for age and weight for age at diagnosis and follow‐up were evaluated with stepwise multiple regression. Correlations with cumulative corticosteroid and radiation dose were examined with Spearman's correlation coefficient. The number and nature of fractures were noted. A BMD Z‐score of below −2 was present in 13 and a BMD Z‐score of −1 to −2 in 31 children. In total, a low BMD was observed in 45% of children. Height for age at follow‐up correlated significantly with BMD Z‐score. Increasing doses of cranial irradiation (18–54 Gy) were associated with lower BMD (p = 0.001, Spearman). This was true also for 22 children with acute lymphoblastic leukemia (ALL) who had received 18–24 Gy cranial irradiation (p = 0.04, Spearman). Fractures occurred in 14 children following trauma. The difference in BMD Z‐scores of children with and without fractures did not achieve statistical significance although the majority of the children with fractures had low BMD Z‐scores. The significant inverse correlation between height for age at follow‐up and BMD must be interpreted with the realization that DXA is not a volumetric measurement of BMD and that short stature is associated with a smaller skeletal mass. Int. J. Cancer Supplement 11:44–47, 1998. © 1998 Wiley‐Liss, Inc.