Dissociation processes of HSi(CH3)(3) have been investigated in the valence and Si:2p core-level excitation/ photoionization by photoelectron-photoion coincidence (PEPICO) and photoion-photoion coincidence (PIPICO) techniques together with synchrotron radiation. Various monocations of H+, H-2(+), H-3(+), CHn+ (n = 0-4), SiCHn+ (n = 0-5), SiC2Hn+ (n = 0-7), and SiC3H9+ are observed in the whole energy range. Partial ion yield and PIPICO spectra were measured as a function of the incident photon energy in the range 65-133 eV. Ab initio calculations are performed to predict the dissociation pathways and their thermochemistry and to provide estimates of the term values of the core-excited states. The variation of the dissociation pattern with the photon energy is discussed in conjunction with the relevant electronic states.