Two-phase flow pattern data were obtained with 12.0 mm bore sight glasses for five refrigerants: R-123, R-134a, R-502, R-402A and R-404A. The existing flow pattern maps of Taitel-Dukler and Hashizume poorly represented the data while the VDI map identified the flow pattern rather successfully, with the exception of mist flows. Methods used in horizontal flow boiling correlations to determine the threshold between all wet wall and partially wet wall flow were shown to be very unreliable.