A 27-month-old boy and a 10-month-old girl with unilateral inflammatory sacroiliitis are described. Both presented with refusal to walk or to stand. Increased erythrocyte sedimentation rate and negative HLA-B27 were found in both cases. There were no laboratory findings to suggest an underlying rheumatic disease. Radiograms of the sacroiliac (SI) joints, lumbosacral spines and the hip joints were normal. Joint/bone scan revealed increased radionuclide activity over the involved SI joints in both cases. Computerized tomograms of the SI joints were abnormal in one patient. Both patients improved with aspirin, recovered and had no sequelae. Inflammatory sacroiliitis appears to be transient and benign. It is a rare event in young children. Possibly some of them are being treated as though they had septic arthritis.