We evaluated the efficacy of common electrical stimulation (ES) types on bacterial growth in vitro using clinically relevant conditions. Four types of ES--continuous microamperage direct current (microADC), high-voltage pulsed current (HVPC), low-voltage monophasic milliamperage pulsed current (LVMmAPC), and low-voltage biphasic milliamperage pulsed current (LVBmAPC)--were each applied to a separate set of culture plates containing Staphylococcus aureus for 1 h at 37 degrees C on 3 consecutive days. After ES treatment, the zone of inhibition surrounding each electrode was measured. Zone of inhibition measurements showed a significant inhibitory effect for continuous microADC and HVPC (p < 0.05), but not for LVMmAPC and LVBmAPC. Differences in bacterial growth inhibition were not found for polarity and time. These data suggest that for infected wounds, HVPC and continuous microADC treatments may have an initial bacterial inhibitory effect, which does not significantly change with subsequent treatments.