In the first part of this paper the effects of introducing specific interface trap configurations into the ideal m.o.s. system are considered while maintaining the condition for equilibrium. The theory is then used to fit an experimental curve and it is found that only three rectangular distributions placed appropriately in the energy gap are sufficient to give close agreement. In the second part the capacitance/voltage relationships are considered of an m.o.s. system biased with a linear voltage ramp of such rate as to generate the quasiequilibrium curve for part of the voltage range, and a nonequilibrium portion for the remainder. A theory is developed for the transition point and the subsequent nonequilibrium behaviour, based on the assumption that interface traps that interact only with the conduction band are the dominating influence. Experimental data are presented which provides reasonable agreement with the theory.