A drive circuit for at least one fluorescent lamp has a half-bridge circuit for production of a supply voltage a resonant tuned circuit coupled to the half-bridge circuit and to which the at least one fluorescent lamp can be connected, a diagnosis circuit with a resistance element coupled to the resonant tuned circuit, at least one current/voltage converter connected to the resistance element that produces at least one measurement voltage from a current flowing through the resistance element, and an evaluation circuit which is connected to the current/voltage converter and is supplied with the at least one measurement voltage and to a method for diagnosis of a fluorescent lamp.