There was a study of mathematical modeling of microstrip oscillators with a substrate in the form of plane layered media based on the use of integral and integro–differential equations of the first kind; there was provided substantiation and the basics of building the algorithms of a numerical solution to the equations; examples of the numerical study of the equations for oscillators and layered media with varied topology were given; the case of microstrip oscillators with finite conductivity was studied; the integral equation for the current of the oscillator was derived and examples of its numerical study for oscillators made of high–temperature superconductors were given.