An atomic force microscope (AFM) is used to measure the magnitude of the effective longitudinal piezoelectric constant(d33)of thin films. Measurements are performed with a conducting diamond AFM tip in contact with a top electrode. The interaction between the tip and electric field present is a potentially large source of error that is eliminated through the use of this configuration and the conducting diamond tips. Measurements yielded reasonable piezoelectric constants of X-cut single-crystal quartz, thin film ZnO, and nonpiezoelectricSiO2thin films. ©1998 American Institute of Physics.