Abstract: A method and apparatus for treatment of spinal deformities, for example, scoliosis, in which a muscle stimulator (pulse generator) is used to apply a preferred form of stimulating impulses to a patient so as to involuntarily cause contraction of particular selected trunk muscle groups to thereby effect a curvature correcting movement of selected spinal vertebrae while minimizing undesirable side effects, such as muscle fatigue. A first integrated circuit timer establishes a selectively variable "on-time" for a burst of pulses while a second such timer sets the "off-time" or interval between bursts. The individual pulses in the burst are initially of narrow width, but succeeding pulses in the group are of increasing width up to a predetermined maximum which maximum level is maintained for a desired time ("hold-time") prior to the termination of the burst. In an alternative embodiment, the stimulating impulses may be gradually decreased in width immediately prior to the pulse generator's effective "off-time".