Two patients experienced agranulocytosis associated with either procainamide or trimethoprim-sulfamethoxazole. Both were treated with filgrastim in an attempt to decrease the duration of agranulocytosis. The first patient received 12 days and the second patient 4 days of filgrastim before white blood cell counts recovered. Published reports both support and refute the efficacy of filgrastim in this setting. The agent may be beneficial in certain cases of this disorder, but further investigation is necessary to determine if it has a definitive role.