Within the framework of a European project, two partial discharge calibrators were circulated to thirteen laboratories for an intercomparison of impulse charge measurements in the range between 1 pC and 500 pC. The deviations of the charge values q reported by the laboratories were, with a very few exceptions, within ±(0.1 pC+0.03·q). Furthermore, the characteristics of several partial discharge measuring instruments were investigated. The indication of some of the instruments showed deviations of more than ten percent from the correct values.