A 11-year-ols boy with 3 months history of back pain was found to have a parathroid chief cell hyperplasia atoperation. Initial roentgenograms showed dense metaphysal lines in the knee and wrist and compression fracturesinvolving the lumbar spine. Two months later extensive generalized osteritis fibrosa cystica developed throughoutthe entire skeleton including the skull. Serum chemistry and parahyroid hormon assay were compared before andafter operation. Primary hyperparathyroidism was not corrected even after the operation and the patient succumbed1 year and 6 months after the initial diagnosis.