A conjecture on the origin of elementary particle masses is discussed, based on the “microuniverse” and quantum state reduction concepts. The reduction of the quantum state of a real particle is understood to take place objectively; in every interaction event with other real particles, the quantum state of the particle is annihilated and a new one is created. In these events, the particle is localised in time and in space, with a maximum precision established by the uncertainty principle. The minimum energy required for this localisation constitutes the chief contribution to the particle’s mass. A further contribution is provided by the self-interaction of the particle during localisation, which occurs within a finite duration. Some algorithms for estimating these two contributions are presented and discussed.