A method for monitoring, from a traction vehicle, a lighting system of a trailer with first lights having at least one brake light, at least one right tail light, at least one left tail light, at least one rear fog light and/or at least one reversing light, wherein the first lights are supplied with electricity from the traction vehicle via electric circuits, and wherein during the monitoring of the lighting system of the trailer, each of the first lights is periodically checked with a first waiting time, the check determining whether the electric circuit having the first light to be checked is closed or not, wherein the first waiting time between two checks of one of the first lights is extended incrementally starting from an initial value for each individual first light if the electric circuit through this first light is not interrupted.