Technical Abstract: A variable flow rate sprinkler applicable to center pivot and lateral-move irrigation systems was constructed and tested in the laboratory. Sprinkler nozzle size was reduced to a fixed amount using a retractable concentric pin in the nozzle bore. Cycling insertion of the concentric pin in the sprinkler nozzle bore provided a time-averaged variable flow rate over a range of 36% to 100% for the nozzle sizes tested. The application pattern radius of the sprinkler tested was reduced approximately 15% under variable flow conditions. Sprinkler drop size distribution was also reduced by engagement of the pin in the sprinkler nozzle bore. Measured flow rates compared well with theoretical flow rates below 28 L/min (7.4 gpm). Results from laboratory testing indicate the variable flow rate sprinkler could potentially be used for site-specific irrigation management with center pivot and lateral-move irrigation systems.