Objective: The aim of our study was to determine the reliability and validity of the Trunk Control Test (TCT) in people with adult neuromuscular diseases (NMD). Subjects: Sixty six people with NMD participated in the study. Methods: Patients were evaluated using the TCT, manual muscle test (trunk, upper and lower extremities), Motor Function Measurement (MFM), Functional Independency Measurement (FIM) and the Rivermead Mobility Index (RMI). Results: Test-retest reliability (intraclass correlation coefficients) was excellent for the TCT. The intraclass correlation coefficient score was 0.979 (95% confidence interval 0.968-0.986). Cronbach alpha value was 0.749, and item-to-total correlation coefficient for "rolling from supine to the dominant side,'' "rolling from supine to the other side'' and "sitting up from lying down'' was (r = 0.61), (r = 0.57) and (r = 0.92), respectively, for construct validity. The TCT was found to be correlated with MFM (r = 0.57), MFM trunk (r = 0.62), trunk muscle strength (r = 0.61), shoulder flexion muscle strength (r = 0.39), hip flexion muscle strength (r = 0.39), FIM (r = 0.35), FIM motor (r = 0.66) and RMI (r = 0.39) for convergent validity. Conclusion: Our results confirm that the TCT is an easy, reliable and valid instrument for the measurement of trunk performance in ambulatory NMD patients.