Neuromuscular stimulation of the abdominal wall muscles can provide respiratory support in tetraplegia, where the main expiratory muscles are affected by paralysis. Stimulation may be applied by simple surface stimulation, resulting in a uniform muscle contraction which can help to improve expiratory function for coughing and breathing. In this review, an overview of methods and approaches available for abdominal muscle stimulation is given. Studies are discussed which show that this technique can lead to improvements in expiratory flow and tidal volume, resulting in enhanced cough and breathing functions. Approaches are introduced which aim to integrate abdominal stimulation with the subject's own voluntary breathing functions. These are illustrated with experimental results from the evaluation of automatic stimulation methods in tetraplegic patients. Clinical significance and applications are discussed and future developments are outlined.