The ion energy distribution in a plasma focus during second pinch compression is derived theoretically. Adiabatic heating during plasma compression and escape of particles through the pinch ends are taken into account. The speed of the pinch compression is determined, with allowance being made for plasma inertia and gas-kinetic and magnetic pressure. It is shown that the ion-energy distribution differs from a Maxwellian distribution. The most marked difference is observed in the tail of the energy distribution, the portion of high-energy ions in the plasma being higher than at thermodynamic equilibrium. Theoretical and experimental results were found to be related.