The available experimental information and semi-empirical scaling properties on total cross-sections for electron impact ionization, dissociative excitation and recombination processes of hydrocarbon molecules and their ions, as well as for proton charge exchange on these molecules, were used to derive unified analytic representations of these cross-sections for all CxHy molecules and their ions with x = 1-3 and 1 less than or equal to y less than or equal to 2x + 2. The procedure for obtaining the partial cross-sections for individual reaction channels of a given process from the presented total cross-sections is outlined. (C) 2003 Elsevier Science B.V. All rights reserved.