An approximate analytical approach for determining the temperature distribution in a hollow cylindrical cup of radiusC, having a base thicknessH, with a stem of radiusA, and lengthL, is given. The outer radial surface of the cup is held at a temperatureT0and the temperature at the bottom of the stem isTs. All other surfaces are adiabatic. This geometrical arrangement is used to observe marker motion under the influence of a large thermal gradient in a thermal diffusion experiment described in the following paper. In this setup, only the sink temperatureTsand the temperature at the bottom of the cupTmcan be measured. Equations are presented which enable one to calculate the temperature and its gradient along the axis of this arrangement with relative ease for the physically important caseA/C<¼. In the region along the axis above the cup‐stem interface, the temperature at any point is given in terms ofTm, Ts, and functions which depend only upon the ratioA/H. A table of these functions is presented for the cases &pgr;A/H=0.4, 0.8, and 1.2.