peer reviewed ; Atypical myoglobinuria in grazing horses was described in United Kingdom and Germany between 1984 and 1996. Fourteen horses were presented at the University of Liege between November 2000 and April 2001, with a clinical history suggesting atypical myoglobinuria. Lesions were similar to those previously described. All horses were at rest and grazing when they developed clinical signs. Three times, the syndrome killed several horses grazing together. Horses were generally found recumbent, nearly or totally unable to stand up. They were presenting tachycardia, polypnoea, myoglobinuria and died rapidly. When performed, blood analysis revealed severe muscular enzymatic activity rises. Histopathology revealed pulmonary congestion and oedema, and squeletal muscular fibers degeneration, mostly in respiratory and postural muscles. These observations are in accordance with cases of atypical myoglobinuria previously described in UK and Germany. The aetiology of this pathology is still unknown, despite of research attempts.