We studied 168 children with acute lymphoblastic leukemia (ALL) and 57 with acute nonlymphoblastic leukemia (ANLL) by retrospectively analyzing clinical symptoms, bone or joint involvement, and hematological findings to verify the clinical features and prognosis of children with acute leukemia who showed radiographic bone changes at the time of diagnosis. Of these, 36 with ALL (21.4%) and 6 with ANLL (10.5%) had symptoms referable to the bones or joints. Thirteen patients (7.7%) with ALL showed bone lesions radiographically. Phenotypically, 12 of the 13 had common ALL, 8 were incorrectly diagnosed and had received treatment for osteomyelitis or juvenile rheumatoid arthritis for 1 to 7 months prior to diagnosis of ALL. Leukocyte count was nearly normal with few or no blasts, and anemia and thrombocytopenia were mild or absent in all patients. Twelve of them remained in a complete remission for 26 to 148 months. Our data suggest that children with bone lesions related to acute leukemia exhibit clinical features that mimic infectious or collagen disease at diagnosis, and may belong to a subgroup of ALL with a better prognosis.