Growth rate measurements were made for water drops grown on nuclei in atmospheric air samples taken in Rolla, Missouri. Rolla, having a population of 15,000 and very little industry, is relatively free of urban pollutants. The measurements were made in a vertical flow thermal diffusion chamber at supersaturations of 0. 5 and 1%. The time to grow from near dry radius to the final radius (6 to 7. 5 mu m) was measured. If one assumes the thermal accomodation coefficient is unity, the measurements indicate an average value of 0. 026 for the condensation coefficient. The temperature ranged from 22. 5 to 25. 7 degree C.