Propene oxide is a building block of the modern chemical industry. The research related to the development of convenient and greener processes has led to the development of the HPPO (hydrogen peroxide propene oxide) process, where propene is oxidized by hydrogen peroxide in the presence of methanol as solvent and titanium silicalite (TS-1) as catalyst. Even if the first industrial plants based on this technology are already running, only few information have been published until now about the kinetics of the process, in particular regarding the side reactions that lower the yields and increase the cost of propene oxide purification. This paper is devoted to the kinetic investigation of both main and side reactions, with the aim to find general kinetic expressions and related parameters.