Nine cases of aneurysmal bone cyst arising in juxtaepiphyseal locations with gross invasion of the adjacent growth plate are reported. In five of these patients an abnormality of growth, due to premature fusion of the affected growth plate, ultimately developed. Treatment of these lesions should attempt to avoid this complication, which appears to be more common than has been appreciated in the past. These nine cases represent 23% of 39 cases of aneurysmal bone cyst occurring in a long bone adjacent to an open epiphyseal plate. This series was extrapolated from a total of 198 cases of aneurysmal bone cyst in the files of the Istituto Ortopedico Rizzoli, Bologna, Italy.