Although patients with Duchenne muscular dystrophy (DMD) have been shown to have decreased total body potassium levels, serum potassium levels have generally been though to be within normal limits. We report two siblings with DMD noted to be hypokalemic in conjunction with a respiratory illness. Hypokalemia may have exacerbated the pre-existing pulmonary insufficiency in these patients. The literature concerning hypokalemia and DMD is reviewed, and recommendations for the closer monitoring of serum potassium levels in patients with DMD are presented.