Following cerebrating ceremony in 20 June 2002, for the completion of Hiuga Sun-Park Hot Spring Bath "Ofunade-no-Yu" facilities, Miyazaki Prefecture, Kyushu Island, 200 neighbors were invited each day to experience bathing on 20 and 21 June. The Bath "Ofunade-no-Yu" officially opened on 1 July 2002. On 18 July, Hiuga Health Center was informed that 3 suspected Legionella pneumonia patients in a hospital and all of them have bathing history of "Ofunade-no-Yu". Health Center officers notified Hiuga City, the main proprietor of the Bath business, that on-site inspection on sanitary managements will be done next day and requested the City to keep the bath facilities as they are. On 19 July, Health Center officers collected bath water from seven places and recommended voluntary-closing of "Ofunade-no-Yu" business. Because of various reasons, Hiuga City did not accept the recommendation and continued business up to 23 July. Because Legionella pneumophila serogroup 1 strains from 4 patients' sputa and several bath water specimens were determined genetically similar by Pulsed Field Gel Electrophoresis of Sfi I-cut DNA. "Ofunede-no-Yu" was regarded as the source of infection of this outbreak. On 24 July, "Ofunade-no-Yu" accepted the Command to prohibit the business. Among 19,773 persons who took the bath during the period from 20 June to 23 July, 295 became ill, and 7 died. Among them, 34 were definitely diagnosed as Legionella pneumonia due to L. pneumophila SG 1, by either one or two tests of positive sputum culture, Legionella-specific urinary antigen, and significant rise of serum antibody titer against L. pneumophila SG 1. In addition to the 8 items shown by Miyazaki-Prefecture Investigation Committee as the cause of infection. Hiuga City Investigation Committee pointed out following 3 items: 1) Insufficient knowledge and understanding of stuffs on Legionella and legionellosis; 2) Residual water in tubing system after trial runs might lead multiplication of legionellae in it; and 3) Inadequate disinfection and washing for whole circulation system prior the experience bathing. The Hiuga City Committee directed 24 measures to improve the sanitary condition of the facility including following 5 items. 1) Fix the manual for maintenance and management of the bath. 2) Keep sufficient overflow of bath water. 3) Put disinfection of filters into practice. 4) Precise measurement and control of the residual chlorine concentration in bath water. 5) Replacement of filtrating material from crushed porous ceramic into natural sand.