A hand-held unit has been constructed for routine measurement of exposure times of argon and krypton lasers. A small photodiode is used as the sensing element, and the measured exposure time in ms is observed on a liquid-crystal display. A series of measurements was made on a set of four lasers in use in ophthalmology departments in North Wales. Typically, the measured exposure times were observed to agree well with set values. Percentage errors were, however, often considerable at the shortest exposure settings. A small variation in values of exposure timings for a selected exposure time was found as a function of selected aiming-beam position. This presumably arises out of the design of the particular aiming-beam/shutter assembly. Although no serious shutter malfunction was detected, the ability to measure exposure times accurately was considered relevant to checking the delivered output of laser systems.