The generator with gel matrix is considered a perspective type for obtaining99mTc. The elution yield of a generator and the course of the elution profile AVn= f(Vn) are affected by the properties and conditions of preparation of zirconium molybdate (generator matrix). Furthermore, it is influended by neutron flux density as well as irradiation time and temperature of cooling water during the irradiation. Zirconium molybdate, Mo: Zr = 1.72, in the form of a monodispersion (mean particle size x = 0.175 mm), was irradiated under the neutron flux density ϱn= (0.7 … 2.2) × 1013cm−2s−1. The elution profile and the elution yield of99mTc were examined in dependence on the temperature of drying the Zr–Mo matrix (40–100 °C). The kinetics of the passage of99mTc into the solution, in dependence on the temperature of drying the hydrogel, was investigated. Some predetermined substitutional functions were tested and the mechanism of the99mTc passage into solution was explained.