Spontaneous and current-induced electrical activity was recorded intracellularly to resolve the controversy whether or not the circular muscle layer of the colon generates spiking activity. Particularly in the first hour after mounting the tissue in the organ bath, spikes were recorded at both the submucosal and the myenteric plexus side of the muscle layer. Spikes were seen as part of the slow wave upstroke in the submucosal surface cells, and spikes occurred both at the upstroke potential and superimposed on the plateau potential in myenteric plexus surface cells. Spikes increased the force of contraction. The study supports earlier claims using extracellular recording techniques that circular muscle cells generate spiking activity, particularly in the presence of depolarizing stimuli, and that spikes contribute to contractile activity.