Breakdown in low pressure radio frequency (rf) plasmas is investigated with particle‐in‐cell simulations in a model gas based on argon. A one dimensional model with a realistic rf wave form is used in a range of pressures between 1 and 50 mTorr. Dynamic scaling and electron generated secondaries are introduced in order to simulate breakdown realistically, and it is possible to follow the discharge development from a few initial electrons to the steady state plasma withne∼109cm−3. The results confirm that breakdown is controlled by the resonant multiplication of secondary electrons known as the multipactor. For the pressures investigated, however, ionization is the main source of new charges and a model based on a typical electron trajectory is introduced to account for the growth in the number of electrons in the discharge gap. The model is in good agreement with the simulation results. ©1996 American Institute of Physics.