Since 23rd August 2003, 20 clustered cases of Legionnaire’s Disease had been recorded, one of which was potentially life-threatening. 17 of the 20 victims were living or working within a zone east of the city stretching 3 km in diameter; 2 of them remained hospitalised. Given the dates when symptoms first appeared, the contamination period lasted from 13th to 21st August. By 29th Aug, the inspection authorities for classified facilities had established, after a crisis response meeting at the Prefecture, an exhaustive inventory of installations within the designated boundary containing cooling circuits. On 29th Aug, the Prefecture issued successive orders suspending use of these installations while awaiting results of analyses and moreover imposed a full bleeding, cleaning and disinfection of all such circuits. Service start-up was contingent on bringing the Legionella concentration below 1,000 CFU/litre. From 30th Aug through 8th Sept, the inspection authorities for classified facilities held 10 inspection visits both to verify that the cooling towers were actually offline and define their classification according to a dedicated nomenclature: 4 were assigned to the mandatory declaration system, while a 5th was not classified. On 8th Sept, the results of analyses on 4 towers from samplings performed 29th Aug (the 5th tower was empty, though the facility operator had conducted a self-inspection 3 days earlier) indicated the following concentrations (in CFU/litre): ice skating rink – 850,000, bank – 30,000, strip mall – 750. On 10th Sept, 3 suspension orders were reissued after analyses on 3 of the 5 sites showed positive results, with steps carried out to determine serotypes and genotypes. Any cooling circuit restart was subject to installing a continuous treatment device with alternation of disinfectants, in addition to requiring 2 samples 10 and 20 days after service start-up. 2 of the 5 cooling towers, with concentrations below the detection threshold, were exempted from these new prescriptions. On 24th Sept, only the skating rink was eliminated as a potential source. On 25th Sept, 2 suspension orders previously targeting the bank and strip mall were extended subsequent to the serotyping results. The genotypes of strains sampled from 4 of the patients and those found in the bank’s cooling tower were identical. Prior to restart, this business underwent an expert appraisal by a certified body; moreover, opening the strip mall to shoppers remained contingent on the genotyping results.