Using noncontact scanning probe microscopy techniques, dielectric properties were studied on 50-nm-length scales in poly-vinyl-acetate (PVAc) and poly-methyl-methacrylate films. Low-frequency(1/f )fluctuations observed in the measurements, peaked in intensity near the glass transition temperature in PVAc. The noise is shown to arise from thermal dielectric polarization fluctuations. Analysis of this noise provides a noninvasive method of probing equilibrium nanometer-scale dynamical processes in dielectric materials and devices. ©1998 American Institute of Physics.