The kinetic growth model for hydrogenated amorphous silicon (a-Si:H) from SiH4 radicals in SiH4 plasmas is reviewed on the basis of recently obtained experimental and computational data. New surface reactions are considered and their implications for the a-Si:H film growth mechanism are discussed. Furthermore, from the experimentally observed substrate temperature-dependence of the bulk hydrogen content and the composition of the a-Si:H surface hydrides, it is concluded that surface processes play an important role in hydrogen elimination from the him during growth.