In this study it has been found that exposure of photosensitized erythrocytes to short, intense electric pulses, resulted in cell lysis. When erythrocytes were photosensitized with increasing concentrations of the photosensitizer, hematoporphyrin derivative (HPD), and subjected to electric pulses in the absence of light, cell lysis increased with increasing photosensitizer concentration. In addition, it has been shown that exposure of photosensitized erythrocytes to electric field pulses of increasing field strength resulted in increased cell lysis. Light activation of photosensitized erythrocytes, pre-treated with electric pulses, also resulted in increased cell lysis. The results presented here suggest that HPD may be activated in the absence of light using electric pulses. We suggest that enhancement of activation by electric field stimulation may find application in increasing the overall efficiency of photodynamic therapy.