OBJECTIVE: To assess the reproducibility of the Berg Balance Scale (BBS) and the Single-leg Stance (SLS), and the validity of the SLS as an independent test of upright postural control in patients with chronic stroke. DESIGN: An intra-rater test-retest reproducibility study. The BBS and the SLS were assessed twice, 7 days apart. SETTING: A university hospital. PARTICIPANTS: Fifty individuals; 6-46 months after a stroke. MAIN OUTCOME MEASUREMENTS: The reproducibility of the BBS and the SLS was evaluated with intraclass correlation coefficient (ICC(2,1)), the mean difference between the 2 test sessions (d̄) with 95% confidence interval (95% CI), the standard error of measurement (standard error of measurement [SEM]%), the smallest real difference (SRD%), and the Bland-Altman graphs. To assess validity of SLS, the relationship between the SLS and the BBS was analyzed by the Pearson correlation coefficient. RESULTS: The ICC(2,1) was 0.88 for the BBS, and the ICC(2,1) values were 0.88 for the nonparetic limb and 0.92 for the paretic lower limb for the SLS. The smallest change that indicates a real improvement for a group of individuals, SEM%, was 3% for BBS, 15% for the nonparetic limb and 27% for the paretic limb for SLS. The smallest real difference for a single individual was 8% for BBS but was higher for SLS, at 42% for the nonparetic limb, and 74% for the paretic limb. There was a significant relationship between the SLS and the BBS (r = 0.65-0.79; P < .001). CONCLUSIONS: The BBS and the SLS are reproducible measurements in patients with chronic stroke, but only the BBS is sensitive enough to follow changes over time or after an intervention. The SLS is strongly related to the BBS and can be used as an independent test to measure upright postural control after a stroke.