Several aspects of the physics of periodically pulsed reactors and boosters are treated on the basis of the point neutron kinetics model. Steady-state operating conditions are established from delayed-neutron precursor and energy balances. The dependence of the power pulse characteristics and, in particular, the power pulse halfwidth on the principal reactor parameters is derived for both types of systems. Relations for the kinetics of pulsed reactors and boosters are given and the relative sensitivities to reactivity changes are discussed. Design examples are given to illustrate the pulse characteristics achievable in practical systems. Physics design requirements and performance limitations for high-power pulsed reactors and pulsed boosters are mentioned