11 November 1979--a day to remember: the Mississauga disaster.

The derailment of a train carrying potentially lethal chlorine, accompanied by exploding tank cars of propane, set into motion the evacuation of the Mississauga Hospital, Queensway General Hospital (Etoblcoke), and Oakville-Trafalgar Memorial Hospital, near Toronto. The method in which the three hospitals, along with the 220,000 residents of Mississauga, were evacuated was so highly efficient and orderly that many now question the necessity of the action. But absence of panic should not be interpreted as an absence of danger. The Economist (17 - 23 November, 1979, volume 273, number 7107) extrapolated data from a British study to show there was enough chlorine in the tank to kill 24,000 people, given the population density in the area of the derailment. The purpose of this article is to describe the involvement of hospital pharmacy in the "Mississauga Saga", and to draw some conclusions from this experience.