TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA new logging-while-drilling (LWD) tool that incorporates directional antennae and long measurement spacings has been developed and field tested. The directional electromagnetic (EM) tool measurements are more sensitive to approaching resistivity boundaries than existing propagation resistivity tools. Combining measurements from symmetrically arranged pairs of antennae further amplify this boundary effect while minimizing undesirable sensitivity to dip and anisotropy. Novel data processing and structure visualization software was developed to aid the decision-making and planning process. Field test results from Oman and the North Sea illustrate how the directional EM measurements fulfill the requirements for geosteering in thin, dipping, and curving targets with lateral resistivity variations. In addition, the directional EM tool also enables improved characterization of resistivity and resistivity anisotropy in high-angle and horizontal wells.