The laboratory and hospital records were reviewed for the 156 children seen at Milwaukee Children's Hospital over a thirty-one month period with erythrocyte sedimentation rates (ESR) greater than or equal to 100 mm/hr. Fifty-five per cent of the children had an underlying infectious disease, 25 per cent had a collagen or renal disease, 13 per cent had neoplasms, and 6 per cent had miscellaneous disease processes. Patients with infectious diseases and high ESRs were significantly younger, significantly more febrile, and had higher leukocyte and absolute band counts than did patients in the other groups. Patients with malignancy had significantly lower hemoglobin levels, leukocyite and absolute PMN counts. Some patients did die during the 30-month study period but not during the particular hospitalization in which the ESR was obtained.