Clinical, roentgenographic, electromyographic, and psychiatric studies of twenty-six patients with voluntary dislocation of one or both shoulders revealed that dislocation was produced by suppression of one element of one of the muscle force-couples responsible for normal shoulder motion, that most patients responded well to muscle-strengthening exercises, that patients with significant psychiatric problems did poorly after all types of surgical and non-operative treatment unless their psychiatric problem had been resolved, and that if surgical treatment was undertaken, a combination of procedures was necessary rather than one of the standard operations.