Maps of the multi-holdup regions in co-current and countercurrent flows are presented in terms of the controlling non-dimensional parameters. These maps clearly demonstrate the symmetrical relationship between upward and downward co-current inclined flows. The feasibility of obtaining multi-holdups in co-current up flow is validated experimentally using oil-water system. The multiple holdups are shown to be associated with hysteresis phenomenon. The introduction of the multi-holdup regions on flow-pattern maps of various gas-liquid and liquid-liquid systems, indicates that these regions correspond to operational conditions where stratified flow was experimentally observed. The significance of multi-holdups phenomena to transition from stratified flow to other bounding flow patterns is discussed. (C) 2003 Elsevier Ltd. All rights reserved.