The purpose of this study was to establish the reliability of the Trunk Impairment Scale (TIS) translated into Korea in patients with stroke. It also aims to score the quality of trunk movement and to be a tool for the treatment. The TIS consists of three subscales that static sitting balance, dynamic sitting balance and co-ordination. The TIS score ranges from a minimum of 0 to a maximum of 23. Twenty-five stroke patients (13 males, 12 females) were examined by two physiotherapists. Interrater and test-retest reliability were assessed. Kappa and weighted kappa values for the items of the trunk assessment of the TIS ranged from .67 to 1.00. Intraclass correlation coefficients for interrater and test-retest agreement were .95 and .97. Cronbach alpha coefficients for internal consistency range from .87 to .97. The TIS provide reliable assessments for the trunk and are valid scales for measuring trunk performance in patients with stroke. TIS can be used as a guideline for treatment and the assessment of quality of trunk activity.