A case-control study was conducted among Italian children treated with a stem cell transplant (SCT). Cases (n = 43) were allogeneic recipients with osteonecrosis, and the controls (n = 129) were matched to the corresponding cases on the basis of survival, SCT center and date of transplant. Univariate analysis showed that older age at SCT (OR 1.39; 95% CI 1.24-1.57), total body irradiation (TBI) (OR 5.73; 95% CI 2.38-13.83), chronic graft-versus-host disease (GvHD) (OR 4.31; 95% CI 2.05-9.07), and duration of steroid treatment after SCT (OR 1.118; 95% CI 1.034-1.209) were statistically correlated with osteonecrosis. However, multivariate analysis revealed that the only factors that were significantly associated with osteonecrosis were older age at SCT (p = 0.0001), TBI (p = 0.001) and chronicGvHD (p = 0.001).