This is the second of three related papers on mixed convection heat transfer in vertical passages with one surface heated and the opposite one unheated. Experiments with water are reported in which local heat transfer coefficients have been determined under conditions of turbulent. buoyancy-influenced, descending and also ascending flow in a vertical passage of annular cross-section having a uniformly heated inner surface and an unheated outer Surface. Effects of variable properties were negligibly small, but influences of buoyancy could be readily produced by increasing the heating and reducing the flow rate. The mode of heat transfer was systematically varied from forced convection with negligible influence of buoyancy to mixed convection with very strong influences of buoyancy. As in the case of the related Study using air reported in the preceding paper, the results obtained demonstrate that the effects of buoyancy oil heat transfer in such a passage generally follow a pattern which is similar to that found with uniformly heated tubes. With downward flow, heat transfer is systematically enhanced in comparison with that for forced convection as a result of increased buoyancy influence and a fully developed thermal condition is achieved more and more readily. With upward flow, heat transfer is either impaired or enhanced depending on the strength of the buoyancy influence. In general, thermal development is then non-monotonic and a fully developed thermal condition is not readily achieved. However. just as in the related study using air. some clear differences are apparent between the present results and those obtained in similar experiments with circular tubes. The onset of buoyancy-induced enhancement and impairment of heat transfer is delayed. the latter Occurs more gradually and the maximum impairment of heat transfer is reduced. Such trends are not unexpected. In a uniformly heated circular tube. modification of the flow and turbulence occurs as a result of influences of buoyancy which are present over the entire surface. However, in an annulus with a heated core and an adiabatic Outer casing only the inner boundary layer is directly affected.