BACKGROUND: Bone involvement represents a common symptom at diagnosis in children with acute lymphoblastic leukemia, and its prognostic value is not entirely clarified. The aim of this study was to evaluate bone involvement at diagnosis in children with acute lymphoblastic leukemia as a predictive factor and to correlate its presence with other demographic, clinical, and laboratory findings.METHODS: We retrospectively reviewed the medical records of 97 children with acute lymphoblastic leukemia diagnosed from January 2005 to December 2014. The mean age of patients was 5.7 years, and 83 (85.6 %) of them were diagnosed with B-acute lymphoblastic leukemia.RESULTS: Among the 97 children, 46 (47.4 %) reported bone involvement at the time of diagnosis. Among children with B-acute lymphoblastic leukemia 43/83 (51.8 %) reported bone involvement, while among children with T-acute lymphoblastic leukemia only 3/14 (21.4 %) (p =0.04). Bone involvement was registered more frequently among males (30/59; 50.8 %) in comparison to females (16/38; 42.2 %) (p =0.414). The mean white blood cell count at diagnosis was lower among children with bone involvement (109,800/mm vs. 184,700/mm) (p =0.092). The mean age of patients with bone involvement was four years, which differs significantly from those without bone involvement (p =0.029). Moreover, children with bone involvement at diagnosis were prednisone "good responders" (79.5 %) when compared with those without bone involvement (58.8 %) (p =0.046). Additionally, mean serum phosphate values were higher at diagnosis among children with bone involvement (5.3 mg/dl vs. 4.8 mg/dl, p =0.035).CONCLUSIONS: The presence of bone involvement at diagnosis is related with immunophenotype of B-acute lymphoblastic leukemia, lower mean age, lower mean white blood cell count and good prednisone response. According to presented data, we conclude that the presence of bone involvement at diagnosis represents a positive predictive factor for outcome/survival. Hippokratia 2016, 20(3): 227-230.