A modification of the standard Sawyer-Tower circuit method of displaying ferroelectric hysteresis allowed the technique to be extended to sinusoidal switching frequencies of 2 MHz. Using this method, probe station measurements of switched remanent polarization were made for two films: excimer-laser-deposited lead zirconate titanate (PZT) and sol-gel PZT. Switched remanent polarization and dielectric constant were measured as a function of frequency between 100 Hz and 2 MHz and as a function of elapsed switching cycles at the 1-MHz rate. Both films showed decreasing switched remanent polarization and dielectric constant with increasing frequencies. This effect is attributed to limitations in domain wall velocity.