We reviewed the records of all patients with a diagnosis of ALL made at our center during a 13-year period to determine the relationship between bone pain and the hematologic findings at diagnosis of acute lymphoblastic leukemia. Of 296 eligible patients, 179 (60%) had no bone pain (group 1), 65 (22%) had some bone pain (group 2), and 52 (18%) had prominent bone pain that overshadowed other manifestations of the leukemia (group 3). Statistically significant differences were found between the groups for hemoglobin concentration (p less than 0.001), leukocyte count (p = 0.014), absolute neutrophil count (p = 0.002), percentage of circulating blast cells (p = 0.009), and platelet count (p less than 0.001). Children in group 3 had values closer to normal for all these values than those of patients in the other groups. Group 3 patients had symptoms an average of more than 2 weeks longer before diagnosis, and had significantly lower serum uric acid and higher calcium levels than patients in the other groups had. No differences were detected among the groups in age at diagnosis, gender, or survival rate. We conclude that children with acute lymphoblastic leukemia who have prominent bone pain preceding the diagnosis frequently have nearly normal hematologic values and that this feature may contribute to a delay in diagnosis.