Nitrogen-containing bisphosphonates (NCBs) are potent inhibitors of bone resorption and are used in the treatment of adults with various skeletal disorders. Little is known about their effects on the growing skeleton. The authors retrospectively studied the skeletal radiographs obtained in nine children before, during, and after NCB administration. Bandlike metaphyseal sclerosis and concentric epi- and apophyseal sclerosis developed in all patients. The extent of sclerosis depended on the duration of treatment and was related to local, and probably general, skeletal growth activity. In the maturing spine, NCBs caused a "picture-frame" or "bone-within-bone" appearance, depending on continuation or cessation of administration. In addition, metaphyseal undertubulation of long bones was noted in five patients. After discontinuation of bisphosphonate treatment and/or closure of the growth plates, the degree of sclerosis decreased, and sclerosis tended to disappear, indicating that this is a reversible phenomenon.