We have measured the effect of a depolarizing field on the properties of a ferroelectric capacitor. By systematically adjusting the amount of charge available to compensate the polarization, we can control the strength of the field inside the ferroelectric. We find that even a few percent of uncompensated polarization charge results in a significant suppression of measured ferroelectric properties, and a complete lack of compensating charge leaves a greatly reduced, although nonzero, polarization. The effect of a depolarizing field is briefly discussed in terms of proposed ferroelectric device applications. ©1997 American Institute of Physics.