In Monte Carlo simulation of semiconductors[1,2] the most laborious part is the calculation of the transition probabilities as function of scattering angle and especially the inversion of these expressions. An obvious way to avoid this is to use look up tables. In many cases, however, this is not possible, e.g. because the parameters change during the simulation. For these cases we propose to use a technique called internal self-scattering which previously has been used only for carrier-carrier scattering. 1. C. Jacoboni and P. Lugli, The Monte Carlo Method for Semiconductor Device Simulation. Springer, Wien (1989). 2. R.W. Hockney and J.W. Eastwood, Computer Simulation Using Particles. McGraw-Hill, London (1981).