BACKGROUND AND PURPOSE: Standardized scales are a prerequisite for rehabilitation and research. This study was designed to determine the reliability and validity of scores on items of the trunk assessment of the Melsbroek Disability Scoring Test (MDST) and Trunk Impairment Scale (TIS) in people with multiple sclerosis (MS). SUBJECTS: Thirty people with MS participated in the study. METHODS: Interrater and test-retest reliability and construct validity were assessed. RESULTS: Kappa and weighted kappa values for the items of the trunk assessment of the MDST ranged from .74 to .95, and the kappa and weighted kappa values for the TIS items ranged from .46 to 1.00. Intraclass correlation coefficients for interrater and test-retest agreement were .93 and .92, respectively, for the trunk assessment of the MDST and .97 and .95, respectively, for the TIS. Bland-Altman analysis showed consistency of scores without observer bias. Construct validity was established. DISCUSSION AND CONCLUSION: The MDST and TIS provide reliable assessments of the trunk and are valid scales for measuring trunk performance in people with MS.