In a remarkable and well known study by Van Konijnenburg and Scott (1980) it was shown that by using the Van der Waals equation and choosing selected molecular parameters, the phase behaviour of most binary systems can be classified within a so-called masterchart according to 5 types, numbered I-V. The study further revealed that phase diagrams which on first sight seemed unrelated, at closer inspection could be transformed into each other by continuous changes in the molecular parameters. One type however, characterized by closed loop liquid-liquid equilibria and indicated as type VI , could not be incorporated in the classification scheme.In this presentation we will first endeavour to clarify the concept of coherence of phase behaviour. To this end we will analyze the phase behaviour of simple liquid mixtures in equilibrium with an ideal vapour phase. The suggested coherence will be shown from a primitive masterchart which is constructed from experimentally accessible properties reflecting resp. 1-2 interactions and 1-1 vs. 2-2 interactions. All sorts of phase diagrams with both small and large deviations from Raoult's law, including azeotropy and/or liquid phase splits, can be shown to transform into each other continuously by continuous variation of the coordinates. Next we include the continuity of the vapour and liquid phase and summarize Van Konijnenburg and Scott's (1980) main results. Apart from the L=V critical curve, a strictly new result in the analysis is the possible appearance of a liquid phase split on approach of the L=V critical region. The concept of continuity of the vapour and liquid phases can now be extended to include the continuity between the various L+L and L+V equilibria, including the critical behaviour. Experimental results from the systematic study of phase equilibria are given to substantiate and illustrate this.From recent results (Van Pelt 1992b) based on an advanced equation of state, we have obtained a much better insight into how to integrate type VI closed loop liquid-liquid equilibria into the masterchart and how this type is associated with the phenomenon that Schneider (1966) called Hochdruck-Entmischung . We suggest that use of an equation of state properly accounting for the presence of directional interactions allows continuous transitions between all these phase equilibria.