Primary hyrperparathyroidism is an uncommon condition with an incidence of 25 per 100,000 in general population. We report a case of 67 year old male with giant parathyroid adenoma, and presented with proximal myopathy. The adenoma was weighing about 40 gms. The histopathology report was atypical adenoma of parathyroid gland. The proximal muscle weakness subsided gradually and the power regained after one year.