The purpose of this study was to optimize and determine the most important abrasive water jet turning (AWJT) operational parameters, such as nozzle diameter (0.75 and 1.3 mm), nozzle feed rate (5, 25 and 45 min(-1)), stand- off distance (2, 10 and 18 mm), abrasive flow rate (50, 150 and 350 g x min(-1)), and spindle speed (500, 1500 and 2500 min(-1)), regarding machining efficiency parameters, namely, average surface roughness Ra (mu m) and material removal rate (mm(3) x min(-1)), using AISI 1050 steel workpieces machined by abrasive water jet turning. Taguchi L-18(2(1) x 3(4)) orthogonal experimental design was used for the experimental design. Adequacy of the predicted linear regression model equations was tested using the method of ANOVA. These model equations were used to optimize the operational parameters of the surface roughness and material removal rate. Machinability charts, indicating the optimum processes with respect to the surface roughness and material removal rate for AISI 1050 steel workpieces, were developed and presented in this study. As a result of experimental studies, it is seen that nozzle feed rate proved to have the most significant impact on surface roughness by 48.7 %. Abrasive flow rate proved to have the most significant impact on material removal rate by 84.6 %. Using a nozzle diameter of 0.75 mm, the average surface roughness was improved while material removal rate decreased.