An instrument for constant current iontophoretic transdermal drug delivery was designed, prototyped, and preliminarily tested in the New Zealand white rabbit. This flexible device has been designed to synthesize several constant current output waveshapes of selectable magnitude, frequency, and duty cycle. The output waveforms include the conventional DC and monophasic pulsed DC, as well as two novel iontophoretic waveforms-a trapezoidal and a symmetrical biphasic pulsed DC. Each waveform was used to deliver an angiotensin-converting enzyme inhibitor transdermally to a rabbit with induced hypertension to compare relative antihypertensive efficacy.<<ETX>>