—Frazier and Neelon describe an interesting case of muscle stiffness and pain in association with oral pentazocine use. Although electromyographic studies and a muscle biopsy were not performed, recurrence of the symptoms with rechallenge is suggestive of a direct effect of the drug. All previous cases of pentazocine-induced myopathy involved intramuscular (IM) injections. Local tissue damage has been postulated as the mechanism of injury. This report raises the possibility that pentazocine may have a more generalized myotoxic effect. Whether the muscle stiffness seen in this patient is a precursor of the fibrous myopathy seen with parenteral use of pentazocine is unknown. Identification and careful study of patients with muscular complaints and oral or IM pentazocine use is needed to clarify the mechanism of injury and identify patients before disabling fibrosis occurs.