OBJECTIVE: To examine the clinimetric characteristics of the Trunk Impairment Scale (TIS). This newly developed scale evaluates motor impairment of the trunk after stroke. The TIS scores, on a range from 0 to 23, static and dynamic sitting balance as well as trunk co-ordination. It also aims to score the quality of trunk movement and to be a guide for treatment. DESIGN: Two physiotherapists observed each patient simultaneously, but scored independently. Each patient was re-examined by one of the therapists. SUBJECTS: Twenty-eight patients in a rehabilitation setting. RESULTS: Kappa and weighted kappa values for item per item reliability ranged for all but two, from 0.62 to 1. All percentages of agreement exceeded 81%. Intraclass correlations (ICC) for the summed scores of the different subscales were between 0.85 and 0.99. Test-retest and interobserver reliability for the TIS total score (ICC) was 0.96 and 0.99, respectively. The 95% limits of agreement for the test-retest and interexaminer measurement error were -2.90, 3.68 and -1.84, 1.84, respectively. Cronbach alpha coefficients for internal consistency ranged from 0.65 to 0.89. Content validity was defined. Spearman rank correlations with the Barthel Index (r = 0.86) and the Trunk Control Test (r = 0.83) was used to examine construct and concurrent validity, respectively. CONCLUSIONS: Analysis of different clinimetric parameters support the use of the TIS in both clinical use and future stroke research. Guidelines for treatment and level of quality of trunk activity can be derived from the assessment.