AbstractAcute myopathy in conditions associated with endogenous or druginduced potassium loss has been reported. We describe six patients with potassium depletion myopathy (P‐DM). The clinical picture included flaccid muscle weakness without sensory loss, myalgia, polyuria, and polydipsia. All the cases had markedly increased serum creatine kinase (CK) levels. The most consistent pathological characteristics were phagocytosis of degenerating muscle fibers plus fiber regeneration. Atrophy of type 2 fibers was observed. Vacuoles and vesicular elements originating from T‐tubules were also encountered. The clinical manifestations and morphological changes had reversed after potassium repletion. Both constriction of vascular smooth muscle and cellular energy failure may be pathogenetic factors in P