On August 23,1988, a fire broke out in a warehouse storing PCBs, forcing the evacuation of 5,500 citizens. Three days later, a specialized clinic was opened to examine and reassure the population. Seventy percent of the evacuated people showed up at the clinic. The aim of this case-control study was to identify the determinants of utilization of this clinic among the evacuated population. Cases and controls were sampled from the cohort of the evacuated adults. Both cases and controls were randomly selected among those who consulted and those who did not consult at the clinic. A logistic regression identified nine predictors of utilization: age, family type of household, annual income less than $40,000, objective and perceived exposure to the toxic smoke, reaction to the risk, perceived scale of the evacuation, number of moves during the evacuation period and consultation elsewhere with a physician. Results showed that the fear resulting from exposure created a stronger motive to consult the clinic than physical symptoms and needs.