Pressure drop during steam condensation is measured experimentally in a large, flattened-tube air-cooled condenser. The steel tube is 5.7 m long, with an elongated-slot cross section with inner dimensions of 216 x 16 mm. Cooling air is provided by 48 axial fans of 120 mm diameter, providing air velocity from 2 - 2.7 m s-1. Tube inclination angle is varied from 0 - 49o downwards, and condensation pressure is varied from 70 - 105 kPa. Pressure drop is measured in two 2.85 m sections along the tube. Pressure drop for the full tube is also measured by difference between inlet and outlet gauge pressure. Pressure drop is found to be very small (<100 Pa) for all test conditions due to the low mass flux (< 5 kg m-2 s-1). Frictional pressure drop is found to increase as mass flux increases, and total pressure drop is found to decrease as inclination increases.