Devices, systems, and techniques for delivering trial stimulation therapy to a patient are disclosed. A trial neurostimulator (e.g., an IMD) may be implanted within a patient to deliver stimulation therapy during a relatively short trial period of time. This IMD may include limited circuitry and be powered by an external power source to minimize the size of the IMD within the patient. The IMD may include a non-hermetic housing capable of protecting the IMD circuitry for the trial period of time. In one example, the IMD may include a secondary coil configured to generate an electrical signal in response to a magnetic field generated by an external primary coil, circuitry configured to generate a stimulation signal in response to the electrical signal, and a non-hermetic implantable housing configured to encase or otherwise house the secondary coil and the circuitry.