OBJECTIVE To study ground reaction forces (GRF) and temporospatial parameters for small and medium size dogs using a pressure sensitive walkway (PSW). We hypothesized that, at a given speed, small dogs would have shorter stance time than medium dogs and that dog height (DH) would influence GRF. ANIMALS 30 healthy, sound dogs were divided into 2 groups, small < 15 kg and medium dog group weighing 15 to 25 kg. PROCEDURES GRFs were measured for both groups at walk and trot using PSW. Muscle mass and joint angles were measured. Data were analyzed using SAS version 9.4. Two groups were compared using 2-sample t test, Wilcoxon rank sum test, and Fisher exact test. RESULTS GRFs were successfully measured in both dog groups for walk and trot. Medium dogs had larger limb girth, more peak pressure, max force, increased stance, swing time, and larger stride length compared with small dogs. Stance time increased as DH increased at walk and trot (r = 0.854, P < .001; r = 0.876, P < .001). Stance time increased as BW (body weight) increased at walk and trot (r = 0.887, P < .001; r = 0.858 P < .001). Inconclusive data was obtained for stride acceleration and velocity. The handler side did not influence results (P > .05). Range of motion (ROM) did not differ among groups. CLINICAL RELEVANCE Results suggested that PSW is a reliable device for small and medium dogs. At walk and at a trot, GRF are smaller in small dogs compared with medium dogs, suggesting that normal reference data for PSW need to take BW and DH into account.