Despite optimal drug treatment, many patients with CHF or COPD still suffer from disabling dyspnea, fatigue and exercise intolerance. They also exhibit significant changes in body composition. Attempts to rehabilitate these patients are often futile because conventional exercise training modalities are limited by the severity of exertional dyspnea. Therefore, there is substantial interest in new training modalities that do not evoke dyspnea, such as transcutaneous neuromuscular electrical stimulation (NMES). Herein, we systematically review the literature that addresses the effects of NMES applied to the muscles of ambulation. We focused on the effects of NMES on strength, exercise capacity, and disease-specific health status in patients with CHF or COPD. We also address the methodological quality of the reported studies as well as the safety of NMES. Manuscripts published prior to December 2007 were identified by searching the Medline /PubMed, Embase, Cochrane Controlled Trials Register, CINAHL and The Physical Therapy Evidence Database (PEDro) databases. Fourteen trials were identified: nine trials that examined NMES in CHF and five in COPD. PEDro scores for methodological quality of the trials were generally moderate tot good. Many of the studies reported significant improvements in muscle strength, exercise capacity and/or health status. Nonetheless the limited number of studies, the disparity in patient populations and variability in NMES methodology prohibit the use of meta-analysis. Yet, from the viewpoint of a systematic review NMES looks promising as a means of rehabilitating patients with COPD and CHF. At least, there is sufficient evidence to warrant more large prospective RCTs.