The piezoelectric and dielectric properties of polarized lead titanate zirconate ceramics were measured between 4° and 77°K. The materials were found to retain strong piezoelectric activity at the lower temperature. For one type of ceramic the planar piezoelectric coupling in liquid helium was about 80% of its room temperature value. Its free relative dielectric constant, measured at 1 kc, rose almost linearly from 380 at 4°K to 1300 at room temperature. The mechanical losses decreased sharply at low temperatures, suggesting a reduction in domain wall mobility.