An experimental study of two-phase flow in a 180 pipe bends with 0.016, 0.022 and 0.03 m and the curvature radii of 0.11, 0.154, 0.21 m, respectively have been carried out. The experiments were conducted under the input superficial phase velocity: air from 0.038 to 5.4m s(-1), water from 0.018 to 0.92 m s(-1) and oil from 0.014 to 0.92 m s-1. The conducted research involved the observation of the forming flow patterns and determination of average volumetric in situ gas fraction. On the basis of the results of experimental flow map was created for gas-liquid flow and a method of calculating gas fractions was established. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.