One problem presented in the oil and gas industry is the production of oil using artificial lift methods when two-phases (liquid-gas) are present. The monitoring and measurement of two-phase flows presents a challenge in engineering, changing continuously depending on the distribution and concentration of the dispersed phase. Computational Fluid Dynamics (CFD) present a solution to determine these parameters in real problems. The objective of this study is to analyze and measure the void fraction at the inlet of an Electric Submersible Pump (ESP) and the effect of the gas in the head delivered by the first stage of this pump. To achieve this, CFD simulations were carried out using the Volume of Fluid (VOF) model, where the void fraction and head was obtained. In addition, a comparison between the head results and experimental measurements was performed. The results showed a higher scatter of the void fraction at higher rotation speeds. On the other hand, the head developed decreased with higher gas flow rates and lower intake pressure. The average error between the experimental results and the numerical simulations was 25.6% and increased with higher rotation speed, probably due to the surging phenomenon present within the pump. © 2015 Elsevier B.V.139 4961