Chlorination of indoor swimming pools is practiced for disinfection and oxidation of reduced compounds that are introduced to water by swimmers. However, there is growing concern associated with formation for chlorinated disinfection by-products (DBPs) in these settings. Volatile DBPs are of particular concern because they may promote respiratory ailments and other adverse health effects among swimmers and patrons of indoor pool facilities. To examine the scope of this issue, water samples were collected from 11 pools over a 6month period and analyzed for free chlorine and their volatile DBP content. Eleven volatile DBPs were identified: monochloramine (NH(2)Cl), dichloramine (NHCl(2)), trichloramine (NCl(3)), chloroform (CHCl(3)), bromoform (CHBr(3)), dichlorobromomethane (CHBrCl(2)), dibromochloromethane (CHBr(2)Cl), cyanogen chloride (CNCl), cyanogen bromide (CNBr), dichloroacetonitrile (CNCHCl(2)), and dichloromethylamine (CH(3)NCl(2)). Of these 11 DBPs, 10 were identified as regularly occurring, with CHBrCl(2) only appearing sporadically. Pool water samples were analyzed for residual chlorine compounds using the DPD colorimetric method and by membrane introduction mass spectrometry (MIMS). These two methods were chosen as complementary measures of residual chlorine, and to allow for comparisons between the methods. The DPD method was demonstrated to consistently overestimate inorganic chloramine content in swimming pools. Pairwise correlations among the measured volatile DBPs allowed identification of dichloromethylamine and dichloroacetonitrile as potential swimming pool water quality indicator compounds.