Prospective serial neurological examinations were performed on 445 consecutive traumatic spinal cord injury (SCI) patients admitted for rehabilitation on an average of 22.8 +/- 15.6 days after injury. Patients were categorized by both the ASIA and Sacral Sparing (SS) definitions of complete SCI, in order to compare the definitions in terms of consistency and prognostic ability. Recovery during follow-up was determined by sensory scores for light touch, sharp/dull discrimination, proprioception, and the ASIA Motor Index Score. Change in complete status was unidirectional using the SS definition and bidirectional using the ASIA definition. Twelve patients with SS complete injuries on initial examination converted to SS incomplete injuries at follow-up. No patients converted from SS incomplete to SS complete injury. Twenty three patients with ASIA complete injuries upon admission converted to ASIA incomplete status and 6 converted from ASIA incomplete status on admission to ASIA complete status at follow-up. For quadriplegics, the average motor recovery for patients changing complete status according to the ASIA definition was 11.7 +/- 10.3, which was significantly less (p less than .05) than the average recovery using the SS definition (group 1), 17.9 +/- 9.3. For paraplegics, the average motor recovery using the ASIA definition, 8.3 +/- 6.7, did not differ significantly from the value using the SS definition, 6.8 +/- 4.0.