ISOGAL is a 15 μm ISOCAM survey of ∼ 12 deg2
in the Galactic Plane interior to |ℓ| = 45°. In combination with IJK data from the near-infrared southern sky survey DENIS, the ISO images allow the first detailed study of stellar populations throughout the inner Galaxy. We present preliminary results from a test observation at ℓ = 45° with 6" pixels and completeness limit 8 mJy. Of the ∼ 3000 sources deg2 detected, about half are KM giants, seen through extinction of up to Av, ∼, 30,while most of the remainder are probably dusty young stars. Although away from bright IRAS regions, the field displays spectacular emission features, and, unexpectedly, a number of regions which are optically thick at 15 μm. The dark regions are presumably dense filaments with Av, >, 25