<div class="htmlview paragraph">The paper presents computer-aided calculation of planetary gear systems in automotive transmissions. We distinguish between two approaches to make the calculations: the direct problem and the inverse problem. The direct problem starts with a given nested gear set, calculated by means of the matrix method. This method, previously used only for nested gear trains consisting of simple planetary gear sets, is extended for computation of the Ravigneaux gear-sets as well. The matrix method-based program is presented.</div> <div class="htmlview paragraph">The inverse problem starts with the known kinematic parameters of a gear set. Two known methods used for defining of structure of nested planetary gear-box are briefly described: the iterative approach and the analytic parametric approach.</div>