A research study evaluating piezoelectric sensors used for collecting Weigh-in-Motion (WIM) data is summarized. The evaluation was sponsored by the Highway Innovative Technology Evaluation Center and consisted of testing the WIM sensors under controlled laboratory and fieldloading conditions in both asphalt concrete (AC) and portland cement concrete (PCC) pavements. The field evaluation of piezoelectric WIM sensors is emphasized. The AC installation was performed at the WesTrack test facility near Reno, Nevada, and the PCC installation was performed at a California Department of Transportation (Caltrans) Heavy Vehicle Simulator test site near Palmdale, California. In addition, a compatibility study of the response of the WIM sensors with different data acquisition systems was conducted at the WesTrack facility. Also, various types of grouts were used in the WIM installations. Results indicated that WIM sensor performance was most dependent on the ability of data acquisition systems to process the raw sensor output accurately.