A 17yo male marriage with uneventful previous history developed generalised myalgias, exercise intolerance, and general fatigue after two dosages of azithromycin (500mg/d) during 3d for febrile infection. Neurologic exam revealed generally reduced tendon reflexes. Serum creatine-kinase was elevated to 25000U/L. Needle-EMG showed short and small, polyphasic motor-units and abnormal spontaneous activity, being interpreted as myositis. Azithromycin was discontinued and he was advised to avoid the fitness studio and to drink plenty of liquids. Myalgias disappeared within two days and CK continuously declined. Azithromycin may trigger rhabdomyolysis in the context of exercise and infection. Azithromycin may be myotoxic why it should be prescribed with caution in exercising and infected patients.