Between January 1, 1994 and December 31, 1997, we evaluated 138 children with displaced supracondylar distal humerus fractures treated by closed reduction and percutaneous pinning. There were 49 type II fractures and 89 type III fractures. Three principal pin configurations were used at the surgeon's discretion: 2 lateral pins (42 fractures), 1 medial and 1 lateral pin (37 fractures), and 1 medial and 2 lateral pins (57 fractures). There was no statistically significant difference in clinical stability between these groups. One type III fracture pinned using two lateral pins showed marked rotational instability. We recommend using two lateral pins when treating type II fractures. Type III fractures should be treated using two lateral pins initially and, if the elbow demonstrates significant intraoperative rotational instability, a medial pin should be added. If a medial pin is necessary, and the ulnar nerve cannot be identified by palpation, a small incision should be made and the pin placed under direct vision.