Specific lectures given at the Environmental Health Center in Cincinnati are presented. Topics covered include: bactericidal efficiency and properties; sewage purification; indicator organisms of pollution; sample collection; bacteria in water; bioassays of toxic wastes; industrial waste disposal standards; conditions of life in natural fresh waters and in polluted waters; studies of higher aquatic organisms; breakpoint chlorination; chemical determinations for sewage; biochemical oxygen demand; sewage treatment processes efficiency; epidemiology of water-borne diseases; government role in control of disease; interpretation of stream pollution data; inventory of water and sewage facilities; rural sewage disposal; sanitary surveys and reporting; sewage treatment plant control tests and operating problems; water quality standards; and mobile laboratory operation.