Samples of the Jefferson City, Missouri, raw and finished water were passed through carbon filters and the contents analyzed for contaminants that may affect taste and odor. Approximately 25 parts per billion of chloroform extractable materials were recovered from both the raw and finished water. Chlorination had little influence on the taste and odor effects. Chemical examination coupled with the taste and odor tests indicated that the odorous materials were of petroleum origin. It was conjectured that treatment at the water plant to specifically remove these materials would materially reduce the taste and odor.