Downhole measurements were successfully made, during the DIANAUT program, in three Deep Sea Drilling Project (DSDP) holes in the North Atlantic, utilizing the wireline re-entry capability of the French logging shuttle Nadia which, seated in the drill re-entry cone, provides a completely stable platform with precise control of depth and logging speed. Logging activities included temperature profiles, borehole televiewer logs, flowmeter measurements, fluid sampling, and a three-component magnetometer profile. The different parameters were measured to study the heat transfer regime and hydrogeological processes within the oceanic crust as a function of age and distance from the ridge axis. Interpretation of the data obtained from holes 333A, 395A, and 534A, drilled in rocks ranging in age from 3.5 to 154 m.y., provide evidence of cold seawater circulation in the upper permeable layer of the young crust (sites 333A and 395A), thus maintaining very low temperatures and heat flow; higher temperatures were obtained from the older crust at site 534A. ¿ American Geophysical Union 1992