This paper deals with connective boiling Of ternary mixtures in vertical tubes, Experiments were carried out in 8.58 m long, 25.4 mm ID. electrically heated test section using an n-pentane/n-hexane/iso-octane mixture (0.31/0.22/0.47 overall mole fraction). Bulk and all temperatures as kell LIS local heat transfer coefficients ere measured. The results were compared with those Obtained using an extension to ternary (and multicomponent) mixtures of the methodology proposed by J.R. Barbosa and G.F. Hewitt [Int. J. Heat Mass Transfer 44 (2001) 1465, 1475] for prediction of forced of binary Mixtures ill Upward annular flow. Interphase transfer of heat and mass is dealt with using convective boiling two formulations: (i) a film method in which the diffusive fluxes are Calculated via a linearly generalised Fick's Law [H.L. Toor. AlChE J. 10 (4) (1964) 460: W.E, Stewart, R. Prober. Ind. Eng. Chem. Fundam. 3 (3) (1964) 224]. and (ii) an effective diffusivity method. Droplet entrainment and deposition are modelled via all interchange model that takes into account the local concentration non-equilibrium between the liquid film and the entrained droplets. As for the binary case, it is claimed that the deterioration in the heat transfer coefficient is due to a combined effect of droplet interchange and mass transfer resistance in the vapour side.