Histochemical examinations of the paravertebral muscles and physiological studies were conducted on 17 patients affected with idiopathic scoliosis. Muscle specimens were obtained by needle biopsy. The specimens were removed from both sides of the apical vertebra of the curve and from vastus lateralis. Staining was as follows: 1. ATPase myosin; 2. capillary; 3. Periodic Acid-Schiff (PAS) for glycogen; 4. alpha-glycerophosphate dehydrogenase; 5. DPNH diaphorase. The physiological studies comprised maximum oxygen consumption, anaerobic threshold, isometric force of the flexor muscles of the elbow and femoral quadriceps muscle, and the flexibility of the lumbar spine, shoulder and hip joints. The histochemical tests of the paravertebral muscles showed muscles with a prevalently aerobic metabolic potential, with no evidence of myopathic changes. The physiological studies showed that at the stage at which these subjects were examined, scoliosis is an organic, not a systemic disease.