This paper was prepared for the 44th Annual Fall Meeting of the of the Society of Petroleum Engineers of AIME, to be held in Denver, Colo., Sept. 28-Oct. 1, 1969. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal, provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Experimental field tests were conducted to study the multiphase flow of gas and liquid [gas-water system] through a small-sized choke in a vertical position. The resulting flow patterns were photographed through patterns were photographed through transparent nipples placed immediately upstream and downstream from the choke. A correlation relating flow rates [gas and water], upstream pressures, gas-liquid ratios and orifice sizes was derived from the experimental data and is presented in this paper. The correlation has a limited range paper. The correlation has a limited range of application and is valid for critical flow conditions. It should be useful for choke sizing for both downhole and surface systems. Introduction Multiphase flow of gas and liquid occurs frequently in the petroleum, chemical and related industries. In the petroleum industry gas-liquid mixtures are transported through vertical and horizontal pipes from the reservoir to the wellhead, from the wellhead to the gas-liquid separator and to the stock tank. The refinery receives the mixture which undergoes further traveling from distillation and separating units to final storage. During both vertical and horizontal flow the well production may encounter restrictions in the form of valves, pipe size reductions and/or purposely placed orifices or chokes. The latter restrictions are placed at the wellhead or at the bottom of the well with the object either to measure the flow rate or to control the flow rate by imposing a backpressure on the formation. The choke or orifice can be used to predict the resulting upstream pressure associated with the new desired flow rate or a correct choke size may be selected for a particular flow rate. This assumes, of course, that a suitable correlation is available. The use of chokes in dual installations allows the production of two zones at bottom through one string of tubing. The two zones are commingled at the bottom through a dual flow choke. This procedure eliminates the need of producing two zones through two separate strings. A very significant consideration is that the correct size of choke to be used to allow the required flow rate from each zone must be accurately known. under this premise the various regulatory bodies permit dual installations to be produced permit dual installations to be produced through one string of tubing.