The compound U-74006F is one of a series of 21-aminosteroids that lack glucocorticoid or mineralocorticoid activity. These potent inhibitors of lipid peroxidation have been specifically developed for the acute treatment of central nervous system trauma and ischemia. This study evaluated the dose-response characteristics and capability of U-74006F to promote functional recovery in cats subjected to compression trauma of the upper lumbar (L-2) spinal cord. Thirty minutes following injury, randomized and investigator-blinded treatment was initiated with the intravenous administration of either vehicle (citrate-buffered saline) or one of eight doses of U-74006F. Initial doses of U-74006F ranged from 0.01 to 30 mg/kg. Subsequent doses consisted of intravenous bolus injections followed by a continuous 42-hour intravenous infusion. Over the 48-hour treatment period, cats received total U-74006F doses ranging from 0.048 to 160 mg/kg. The animals were evaluated weekly for neurological recovery based upon an 11-point behavioral scale. With the exception of two cats in one group, the animals receiving accumulated doses of U-74006F (ranging from 1.6 to 160.0 mg/kg/48 hrs) exhibited nearly 75% of normal neurological function by 4 weeks after injury. Lower total doses of 0.16 and 0.48 mg/kg/48 hrs were associated with approximately 50% return of normal function, which was not significantly better than the recovery in the vehicle-treated control group. The lowest total dose tested (0.048 mg/kg/48 hrs) gave results indistinguishable from those in vehicle-treated cats, which had recovered only 20% of their preinjury neurological function by 4 weeks. These findings demonstrate that over a 100-fold range of doses, U-74006F has a remarkable capacity to promote functional recovery in spinal cord-injured cats.