THIS STUDY COMPARES 5 WELL-KNOWN TWO-PHASE pressure drop MODELS IN HORIZONTAL CHANNELS AND PRESENTS ONE OF THEM AS AN OPTIMUM MODEL. IN ORDER TO REACH THIS AIM A SET OF DATA POINTS WHICH CONTAINS 90 POINTS IS USED. THIS SET OF DATA POINTS COVERS 6 FLUIDS (CO2, R-134A, R-22, R-236EA, R-404A, R410A) WHICH THE RANGES OF DIAMETERS, MASS FLUXES AND VAPOR QUALITIES ARE 1.4-6.1 MM, 200-400 KG/M2.S, 0.1-0.9, RESPECTIVELY. THESE MODELS ARE COMPARED WITH 3 DIFFERENT METHODS WHICH USE MEAN ABSOLUTE ERROR (MAE), RELATIVE PERFORMANCE FACTOR (RPF), AND PERCENTAGE OF DATA WHICH FALL BETWEEN ±30% ERRORS BANDS TO COMPARE THEM. ALL METHODS GIVE SIMILAR RESULTS AND PRESENT THE MULLER-STEIN HAGEN AND HECK MODEL AS THE MOST ACCURACY MODEL IN ALL.