&NA;A mathematical model was constructed to predict motor performance in rats for 8 weeks after spinal cord injury. The model is based on experimental data generated from an investigation of the static‐load technique of inducing cord injury and was derived using multiple linear regression. The regression coefficients for weight of the injury‐producing load were statistically significant (P< 0.001), and it was found that the weight of the load contributes over 95% of the posttrauma motor deficit, whereas the time duration of the load resting on the cord contributes less than 5% to the deficit. Sex, pretrauma motor performance, and pretrauma body weight are insignificant covariates. The model may be used to establish expected motor deficits and to derive dose‐response curves. (Neurosurgery19:763‐766, 1986)