The vertical two-phase cross-flow was studied on the shell side of a horizontal tube bundle. The section used consists of 5 tubes with 20mm dia. The tubes are arranged in 10 rows on a square pitch with a pitch ratio of 1.5 in a rectangular shell. Adiabatic flows of air water mixtures were tested in a large superficial velocity range, for liquid (0.001 0.65 m/s) and for gas (0.047 9.3 m/s). respectively. Flow patterns were established and visual observation together with photographic data and a video-film were used. These results, existing flow pattern data and flow pattern maps for the cross-flow in tube bundles were employed to work out a general flow pattern map.