Background Evidence for effectiveness of transcutaneous electrical nerve stimulation (TENS) is still inconclusive. As heterogeneity of chronic pain patients might be an important factor for this lack of efficacy, identifying factors for a successful long-term outcome is of great importance. MethodsA prospective study was performed to identify variables with potential predictive value for 2 outcome measures on long term (6months); (1) continuation of TENS, and (2) a minimally clinical important pain reduction of33%. At baseline, a set of risk factors including pain-related variables, psychological factors, and disability was measured. ResultsIn a multiple logistic regression analysis, higher patient's expectations, neuropathic pain, no severe pain (2 pain locations) and intermittent pain were positively and independently associated with a minimally clinical important pain reduction of33%. ConclusionThe results showed that factors associated with a successful outcome in the long term are dependent on definition of successful outcome.