Pressure drops in two phase flow is generally foreseen by subdividing its value in three terms. In following this procedure and in order to avoid the exact prediction of the mixture density, we have preferred the energy balance method, instead of the more usual momentum one. The comparison of pressure drop data of mixtures flowing upflow, both in adiabatic and diabatic conditions, has revealed that they keep the same behaviour, at least up to the heat transfer crisis, with a progressive lower value for diabatic data beyond this condition. The Cesnef correlations (number 2 and 3), which foresee these pressure drops, were developed in our Department in the past, yielding satisfactory predictions, though having some drawbacks; a new simpler version has been developed, named Cesnef 4. A comparison with other three well known correlations, carried on by predicting about 11,000 data, confirms its better performance.