A heat exchanger tube has a first asymmetrically corrugated sheet portion having an opposite pair of longitudinally extending side edge portions, a plurality of substantially transversely extending ribs and a substantially uninterrupted inner surface, a second asymmetrically corrugated sheet portion having an opposite pair of longitudinally extending side edge portions, a plurality of substantially transversely extending ribs and a substantially uninterrupted inner surface, and at least one joint for connecting side edge portions of the first and second corrugated sheet portions forming a tube and providing an internal flow path for a first fluid and a plurality of external flow paths for a second fluid.