The results of over 200 density and 400 (at 37 sites) in-situ magnetic susceptibility measurements from southeastern New Brunswick are presented. Intrusive rocks were found to be homogeneous in density and to have values similar to those reported from adjacent areas of the Northern Appalachians. However, most of the Coldbrook volcanic rocks show considerable variability in density values even within individual rock types. As expected, rocks containing higher proportions of ferromagnesian minerals (i.e., basalt, diorite, and gabbro) generally gave higher magnetic susceptibility values. The lack of aeromagnetic anomalies over mafic volcanic rocks in the central Caledonia Highlands may possibly be explained in terms of thin and flat-lying flow units.