We report measurements of the conductivity and dielectric constant as a function of frequency and temperature on samples of La2CuO4 from dc to 100 GHz. An analysis of the frequency dependence of the complex conductivity indicates that the high-frequency dielectric constant is large (50) and weakly temperature dependent. The dc charge carriers are massive (1100me), weakly damped, and partially pinned. © 1989 The American Physical Society.