Downhole physical property measurements obtained using standard oil field logging tools in ocean crust hole 396B (leg 46) of the Deep Sea Drilling Project indicate that for the upper 200 m of oceanic layer 2 near the mid-Atlantic ridge in situ sonic velocities, densities, and electrical resistivities are significantly lower and the porosities significantly higher than laboratory measurements on the recovered basalts. In situ sonic velocities vary from about 1.5 to about 4.8 km/s with a mean of about 3.1 km/s. Densities vary from about 1.55 to about 2.6 g cm-3. Porosities are unexpectedly high, ranging from about 13% to about 41%. Electrical resistivities vary from about 5 to about 90 ohm-m. The mean sonic velocity is typical of values obtained for the upper part of oceanic crust of the age at this site (middle Miocene) using marine seismic refraction techniques. Laboratory values for small ocean ridge basalt samples are typically much higher, about 6 km/s. The agreement between refraction and logging velocities, combined with the lack of radial variation in electrical resistivity away from the hole, indicates that formation damage due to drilling is relatively minor and that the values obtained by logging more nearly reflect the true in situ values than laboratory measurement. The major lithologic boundaries can be detected using each of the tools, and combinations of tools can differentiate between rock types. The high in situ porosity and relatively low in situ electrical resistivity imply that this part of the crust contains extensive large scale porosity and is probably quite permeable. Most of the porosity probably occurs between uncemented or weakly cemented pieces of pillow basalt, which makes up most of the upper crust at this site.