The concentration profiles for turbulent flow were determined using a radiotracer technique. An experimental test device was constructed and sodium-24 was used as the tracer. Methylene-blue was also used for a comparison of the results. Samples were taken from different radial planes. The mean squared displacement was calculated and compared with the data of Taylor and Middleman [Taylor, A.R., Middleman, S., 1974. Turbulent dispersion in drag-reducing fluids. AIChE Journal, 20(3), 454-461]. It was shown that the radiotracer technique could be applied successfully to turbulent flow in vertical pipes. (C) 1999 Elsevier Science Ltd. All rights reserved.