Computer programs (in BASIC), are described that predict profiles of solutes (NH4-N, DO) in river sediments, from which the benthic solute flux across the water/sediment interface can be calculated. The programs are based on numerical solutions to the equations of a mathematical model in which the solute is subject to a combination of mechanical dispersion, and linear (zero-order or first-order) or non-linear ("Monod, no growth") distributed sources and sinks. Sensitive model calibration can be obtained if benthic chamber data are used, in which case a surface flux boundary condition is required, instead of the usual surface concentration boundary condition. Instructions, and example problems, are given on the use of the programs. Program output can be displayed immediately on graphics terminals. The program could easily be adapted for other solutes, and other source/sink terms.