Five of seven children who were managed for osteopetrosis had either cervical spondylolysis or lumbar spondylolysis, or both. Three of the children had lumbar spondylolysis only, one had cervical spondylolysis only, and one had spondylolysis in both areas. The five patients were followed for an average of forty-one months (range, sixteen to seventy-two months) after the diagnosis of spondylolysis was made. Three of the patients were managed non-operatively with a lumbosacral corset or a thoracolumbosacral orthosis. One of these three patients, who also had cervical spondylolysis and neck pain, had a posterior cervical arthrodesis, but a stable pseudarthrosis developed. All five patients were asymptomatic at the latest follow-up evaluation, although two had had prolonged low-back pain.We believe that cervical or lumbar spondylolysis is present in children who have osteopetrosis more often than has been previously recognized. The spondylolysis in such children often is associated with low-back pain. The symptoms may be part of the initial presentation that leads to the diagnosis of autosomal dominant osteopetrosis. In one patient, the spondylolysis was associated with a grade-I spondylolisthesis at the time of presentation. This was the only patient who had a slip, and the slip did not progress.