The small intestinal electrical control activity (ECA) was driven by an electrical stimulus and the resultant effects on the frequency and the phase relationships of control waves recorded. The small intestinal ECA can be driven from all sites from which it could be recorded. The mean maximum driven frequency (MDF) was the highest near the pylorus and it decreased distally, but at any given site it was the same before and after dividing the small intestine into small segments. The length of the frequency plateau decreased and phase lag per cm increased with an increase in plateau frequency. The direction of phase lag was orad proximal to a stimulation site and aborad distal to it. Intravenous atropine (up to 100 mug per kg) or reserpinization of dogs before an experiment had no effect on the MDF in the frequency plateau region. The study confirms the validity of an array of bidirectionally coupled relaxation oscillators as a model of small intestinal ECA and shows that the frequency and the phase relationship of small intestinal control waves can be altered by electrical stimulation. The study also points out some differences between the small intestinal and gastric ECA's at the cellular level.