Haff disease, first identified in Europe, is unexplained rhabdomyolysis in a person who ingested fish within the 24 hours before onset of illness. Cases of Haff disease after the consumption of fresh water fish have never been reported in China but have been frequently reported from the Baltic region. We first describe five cases of muscle weakness and rhabdomyolysis that occurred after eating crayfish in China and discuss the different epidemiologic and etiologic aspects of this disease.