The paper describes tests boiling R113 at atmospheric pressure in upward flow over a 17 row column of square pitched electrically heated tubes. Uniform heat fluxes of 10-65 kW m(-2) and maximum Reynolds numbers, Re-max, between 7800 and 27000 were used. The data at the lower heat fluxes of 10 and 20 kW m(-2) consistently exhibited a linear increase of heat transfer coefficient, h, with quality, the slope lower at 20 kW m(-2), so that h at 10 kW m(-2) exceeded that at 20 kW m(-2) and both reached h at 40 kW m(-2) for the maximum quality tested. At the higher heat fluxes a nucleate boiling controlled region was observed at low quality, with h equal to the value at the same heat flux as observed with an isolated tube in a pool, followed by a rise in h at higher quality. The results were compared with the work of other researchers. Heat transfer coefficients for q ≥ 40 kW m(-2) were predicted to an average r.m.s. deviation of 7%, using the asymptotic flow boiling model. However, the sensitivity of h to change of quality and flowrate predicted was much lower than measured and in some cases exhibited opposite trends.