This article discusses the motion of particles in multiple time dimensions and in multiple space dimensions. Transformations are presented for the transfer from one inertial frame of reference to another inertial frame of reference for the case of multidimensional time. The implications are indicated of the existence of a large number of time dimensions on physical laws like the Lorentz covariance, CPT symmetry, the principle of invariance of the speed of light, the law of addition of velocities, the energy-momentum conservation law, etc. The Doppler effect is obtained for the case of multidimensional time. Relations are derived between energy, mass, and momentum of a particle and the number of time dimensions in which the particle is moving. The energy-momentum conservation law is formulated for the case of multidimensional time. It is proven that if certain conditions are met, then particles moving in multidimensional time are as stable as particles moving in one-dimensional time. This result differs from the view generally accepted until now [J. Dorling, Am. J. Phys. 38, 539 (1970)]. It is proven that luxons may have nonzero rest mass, but only provided that they move in multidimensional time. The causal structure of space-time is examined. It is shown that in multidimensional time, under certain circumstances, a particle can move in the causal region faster than the speed of light in vacuum. In the case of multidimensional time, the application of the proper orthochronous transformations at certain conditions leads to movement backwards in the time dimensions. It is concluded that the number of different antiparticles in the k-dimensional time is equal to 3 k À 2 k . Differences between tachyons and particles moving in multidimensional time are indicated. It is shown that particles moving faster than the speed of light in vacuum can have a real rest mass (unlike tachyons), provided that they move in multidimensional time. Ó 2012 Physics Essays Publication.R´esum´e: L'article traite du mouvement des particules dans un temps et espace multidimensionnels. Les transformations de r´ef´erentiels inertiels d'un syst`eme`a l'autre sont d´eduites dans un temps multidimensionnel. Les cons´equences de l'existence d'un plus grand nombre de dimensions temporelles sur les lois physiques sont d´emontr´ees: sur l'invariance de Lorentz, sur la sym´etrie CPT, sur le principe de l'invariance de la vitesse de la lumi`ere, sur la loi d'accumulation des vitesses, sur la loi de conservation de l'´energie-impulsion etc. L'effet Doppler est obtenu dans un temps multidimensionnel. Les corr´elations entre l'´energie, la masse, l'impulsion d'une particule donn´ee sont d´eduites, ainsi que le nombre des dimensions temporelles dans lesquelles cette particule se meut. Formul´ee`a´et´e la loi de conservation de l'´energie-impulsion en cas de temps multidimensionnel. Il est d´emontr´e que si ont´et´e satisfaites certaines conditions, les particules qui se d´eplacent dans un temps multidimensionnel sont tout aussi stables que les particules ...