To evaluate the influence of patient's weight on rehabilitation results after first stroke. Retrospective, comparative study. The sample comprised 84 males and females, first-time stroke patients, who had been hospitalized in the department of rehabilitation at the Hartzfeld Geriatric Hospital, Gedera, Israel for a full 3 mos and who, on admission, had scored between 40 and 60 on the total Functional Improvement Measure (FIM) test. We evaluated the difference in total FIM improvement between normal-weight, overweight, and obese patients. The relative improvement of FIM score was significantly higher in normal-weight patients than in overweight patients, and improvement in overweight patients was significantly higher than in obese ones. We also found a statistically significant negative correlation (r = -0.27, P = 0.014) between relative improvement of FIM score and body mass index (BMI) in the total sample. Our study revealed that during the first 12 wks, rehabilitation is statistically significantly less effective in overweight and, particularly, in obese patients (evaluated by BMI). We also found a statistically significant negative association between the individual's BMI and relative improvement of the FIM score, representing the functional status of the stroke patient.