In order to study the vertical migration of anthropogenic 137Cs, soil inventories ofthis radionuclide were measured in two regions selected on the basisof a previous comprehensive survey in the northern Iranian provinceof Guilan located in the South Caspian region. Ten sampling stations were randomly chosen in these regions and split-level samplingwas carried out to a depth of 30 cm. Sample analysis was performedusing a HPGe detector system. In situ gamma measurementsin both regions were als o carried out with the aid of a portable germanium spectrometer.The experimental data were then compared with the solution of theconvection-dispersion equation (CDE) with the proper initial and boundary conditions to evaluate initialdeposition as well as transport parameter values. The solution,including the effects of both considered sources, i.e. global falloutand Chernobyl releases, fits the measured data well. The effectiveconvection velocity and dispersion coefficients of 137Cslie in the range of 0-0.25 cm·y-1 and 0.32-0.75 cm2·y-1, respectively, indicating a very slow migration rate in the area. Most of the deposited 137Cs still remainedin the top 10-cm layer. Moreover, the fitted depth profiles werethen employed to correct the surface activities of 137Csestimated by in situ measurements.