Flow visualization photographs and measured local heat transfer data are presented for annular film-flow boiling of saturated liquids in a vertical channel with offset strip fins. A special test section was used in this study which permitted direct visual observation of the boiling process while simultaneously measuring local heat transfer coefficients at several locations along the channel. One wall of the channel was heated while the opposite and lateral walls were adiabatic. Measured local heat transfer coefficients on the heated portion of the channel wall were obtained for convective boiling of water, methanol and n-butanol at atmospheric pressure over wide ranges of mass flux and quality. Photographs of the flow indicate that virtually no nucleate boiling is present when the flow is in the film-flow regime. For the fin matrix studied here, complete dryout of the film on the heated surface was not observed to occur at a single downstream location. Instead, dry patches are observed to form at specific locations in the matrix, with the patches increasing in size with downstream distance until the entire film is gone. An approximate analytical model of transport in the liquid film is also presented. A closed-form correlation for the boiling heat transfer coefficient is derived from this model which is in good agreement with our measured data.