Flow pattern data for horizontal intube flow boiling are presented for refrigerants R-134a and R-402 (60/2/38). The flow pattern observations were compared with various criteria for determining whether the entire circumference of a horizontal evaporator tube is wet or only partially wet, an important aspect of predicting flow boiling heat transfer coefficients. Use of only the liquid Froude number FrL (utilized by numerous flow boiling correlations) is shown to be too simplistic and not reliable. A new semi-empirical method of Klimenko and Fyodorov appears to be promising. The observed flow patterns were also compared to several flow pattern maps, showing limited success.