The present study investigates the two-phase flow pressure drop across 90 degrees vertical elbows. The elbows, positioned in the vertical-upward to horizontal and horizontal to vertical-downward orientations, have an inner diameter of 50.8 mm and a radius of curvature of 152.4 mm. Experiments were performed in a wide range of flow conditions at different axial locations and flow orientations to measure the local gauge pressure and void fraction. It is observed that increasing the liquid-phase or gas-phase velocity increases the local gauge pressure. The experimental data are used to study the elbow orientation effect on pressure drop and develop predictive method for two-phase flow pressure drop across 90 degrees vertical elbows. The pressure components due to friction and geometry effects (form loss), gravity and acceleration or deceleration of the two phases are estimated accurately with the detailed experimental data. Then, predictive methods for each pressure components are investigated. For estimation of the pressure component due to friction and geometry effects, six models are evaluated, and the model coefficients are determined from the experimental data. The evaluation results show that the modified Kim et al. correlation and Bowden and Yang correlation can predict pressure drops across both vertical elbows through adjusting the parameter C and the newly introduced minor loss factor. Both models demonstrate negligible dependence on flow regimes. However, the Kim et al. correlation gives closer prediction to the experimental data than the Bowden and Yang correlation, and thus is recommended for prediction of the pressure component due to friction and geometry effects. The other models need further modification to predict the two-phase flow pressure drop across elbows. Published by Elsevier Ltd.