A collective nitrous fumes poisoning (five cases) is reported. Two patients (case 3 and case 4) were comatose, in severe respiratory distress. Shock and slate blue cyanosis were noted. Physical examination and chest X ray revealed acute pulmonary edema-Methemoglobin levels were 71,3% (case 3) and 58% (case 4). Despite treatment both of them died from severe hypoxia resulting in cardiorespiratory arrest. Post-mortem examination was performed upon these four men. On admission the last one (case 5) was conscious, and in good hemodynamic condition. Acute pulmonary edema and cyanosis were present. Methemoglobin level was 37,3%. This patient recovered appropriate therapy. For case 1 and 2 acute anoxia due to methemoglobinemia seems to be cause of death. For cases 3 and 4 death is due to hypoxemia associated with pulmonary edema.