kukaslxctrl is an open-source library for controlling KUKA robots from within the MATLAB Simulink computational environment. kukaslxctrl is designed to communicate with KUKA KRC4 controllers via the KUKA Robot Sensor Interface (RSI), at rates up to 250 Hz. It currently supports sending of Cartesian position commands, and monitoring of system Cartesian and joint positions. Ongoing work on kukaslxctrl aims to increase & streamline the range of interaction interfaces available for the robot, and also to provide more sophisticated library blocks such as preconfigured closed-loop controllers and application examples. kukaslxctrl is available under the MIT license at https://github.com/mitmedialab/kukaslxctrl. It has been tested under MATLAB R2016b. It requires the Desktop Real-Time library for Simulink.