'Introduction'. Tizanidine, an (_2-noradrenergic/imidazoline agonist, and baclofen, a GABAb agonist, have been shown to have both antinociceptive and myorelaxant effects. In this study, the relative effect of tizanidine and baclofen on motor performance was tested at comparable analgesic dosages in rats. 'Methods'. Analgesia was measured using the tail-flick test and an analgesic index was calculated based on the cumulative increase in tail-flick latency. Motor performance was measured from kinematic analysis of swimming and a performance index was calculated based on the cumulative decrement in swim speed. Drugs, tizanidine and baclofen, were administered intraperitoneally following three baseline measurements at twenty minute intervals and subsequently monitored at regular twenty minute intervals for a period of two hours. Three comparable dosages were identified based on analgesia: low dose (0.5mg/kg tizanidine and 2.0 mg/kg baclofen), mid dose (1.5 mg/kg tizanidine and 5.0 mg/kg baclofen), and high dose(3.0 mg/kg tizanidine and 6.0 mg/kg baclofen. (Abstract shortened by UMI.)