Since the summer of 1983, Georgia Tech and NOAA have been engaged in a program whose purpose is to measure, the effects of atmospheric turbulence on the propagation of millimeter waves (MMW). Five different measurement sessions have been conducted, and observations have been made in clear air, rain, fog, and snow at frequencies of 116, 118, 142, 173, and 230 GHz, so that results have been obtained on or near all atmospheric features of interest in this range, including to 118 GHz oxygen line, the 140 GHz window, the 183 GHz water line, and the 230 GHz window'. These measurements have been made over a 1.4 km path at a site near Urbana, Illinois, chosen for its exceptional flatness. Figure 1 is a diagram of the layout of the experiment site and Figure 2 is a photograph of the propagation path looking from transmitter toward receiver. In making measurements of this type, it is important that the path and surrounding terrain be flat, homogeneous, and free of trees or other obstructions, to avoid perturbation of the atmospheric fields. The following sections discuss the equipment used to make these measurements and give some preliminary results.