Objective. Dynamic carpal tunnel syndrome (CTS) is a subtype of CTS in which symptoms usually subside with rest and return with repetitive motions. In this subgroup, nerve conduction studies, performed at rest, are often inconclusive. In this study, the diagnostic value of provocative sonography was evaluated in patients with dynamic CTS. Methods. Twenty wrists of 13 patients with dynamic CTS and 10 control subjects were investigated with sonography before and immediately after provocative exercises imitating work-related stresses. In addition to conventional indices (palmar displacement, nerve area at the middle level, and swelling ratio before and after exercise), 2 newly formed indices (provocative nerve area ratio and provocative palmar displacement ratio) were investigated. Results. In the pre-exercise period, there were no significant differences between patients and control subjects regarding palmar displacement and the swelling ratio. The difference was significant (P = .035) for the nerve area at the middle level. In the post-exercise period, all parameters were significantly different between patients and control subjects. The nerve area at the middle level and the swelling ratio had higher significance (P < .0001) than palmar displacement (P = .015). The post-exercise swelling ratio had the highest sensitivity (95%) in diagnosing dynamic CTS when a cutoff value of 1.26 was used. The provocative palmar displacement ratio had high sensitivity (80%) and the highest specificity (90%) for a cutoff value of 1.28. Conclusions. Provocative exercises increase sensitivity and specificity and contribute to the sonographic diagnosis of dynamic CTS. This examination should be performed if electrodiagnostic test results are negative.