During 1978-79, a seismic refraction experiment was carried out in the Rhenish Massif, West Germany, and adjacent areas, extending through Belgium and Luxembourg into the Paris Basin in France. The experiment was designed to investigate the structure of the crust and uppermost mantle beneath the massif and thus help in a multidisciplinary study, sponsored by the Deutsche Forschungsgemeinschaft, into the causes and mechanisms of uplift of the massif. The Aachen-Baumholder (L1/L2-M1/M2) profile was completed in May and August, 1978. The 600 km long, main profile and the cross profiles, B-K and K-F, were completed in May 1979. During the main experiment in May 1979, 137 recording units of the MARS type from various European countries participated. 20 shots were fired in 1979 and thus a total of 2740 three-component recordings were made.