ABSTRACT A Measurement While Drilling (MWD) system is now available to provide more downhole measurements than ever before. The measurements currently made near the bit, while drilling is in progress, include: formation radioactivityformation resistivityannular temperaturedownhole weight on bithole deviationazimuthtool face angle These geological and engineering measurements are transmitted via a continuous pressure wave through the mud inside the drill pipe. The signals are detected at the surface, where they are processed by an on-site computer. Information is plotted in real time on continuous multi-scale logs, presented digitally on video displays, printed out in hard copy, and stored on magnetic tape. This paper briefly discusses the MWD system that provides these downhole measurements in real time during drilling. Citing actual logs, the paper focuses on specific examples of how these measurements are being used to aid in formation evaluation and to improve drilling control at the well site.