This article presents river-water fouling rates at 12 Tennessee Valley Authority (TVA) power plant condensers, nine of which were retubed with a commercially available enhanced tube. Four were located on the Cumberland River, six on the Ohio, and two on the Clinch River The overall heat transfer coefficients were calculated from logged field data taken over periods extending from 1 to 10 years. The fouling resistances were next calculated with the separate resistance method and with a bundle correction factor to the condensing, single-tube Nusselt prediction. The bundle correction factor was determined for each condenser using the data taken within 1000 hours after each cleaning. With the use of this new bundle factor method, fouling rate data can be obtained even with variable operating conditions. The fouling rates with the enhanced tubes ranged from about the same as to about twice that of the plain tubes. However, the thermal performance with the enhanced tubes remained superior to that obtained with plain tubes for more than a year without cleaning. Also after one year of operation, the enhanced-tube fouling resistance values were less than the minimum value of the TEMA Standards for river water, and the plain-tube fouling resistance values were always less than one-half of this value. After shutdown and brush and/or acid cleaning, the thermal performance values for both the plain and enhanced tubes were restored to essentially the new, clean levels.