Abstract: A laser rangefinder, where the laser is of the passive Q-switched type, is functionally tested. In a method and apparatus for functionally testing the laser rangefinder, the excitation voltage for actuating the laser is raised above the normal voltage, so that the laser sends two light pulses where it normally sends a single one. The pulses are respectively interpreted as a pulse sent from the rangefinder and as a received reflected pulse. A high-voltage unit for providing the excitation voltage is coupled with a feedback circuit in which there is included a voltage divider provided with a switch such that during testing the excitation voltage can be increased so that the laser sends the two required light pulses.