Five adult monkeys (Macaca fuscata) were trained for the go/no-go hand movement task with discrimination between two different color stimuli. The go stimulus was accompanied by a reward when a monkey lifted a lever by wrist extension within the stimulus duration (500 ms). Whereas the no-go stimulus was not. The monkey revealed the potential specific to the no-go response in the prefrontal cortex, called 'no-go potential', i.e. surface-negative, depth-positive deflexions in the cortex of the dorsal bank of the principal sulcus and of the rostroventral corner of the prefrontal region. Effects of electrical stimulation of these prefrontal areas upon the go response were observed and analyzed in order to study functional significances of the no-go potential. The surface and depth (2.0-3.0 mm) electrodes chronically implanted respectively in various cortical areas of both hemispheres, originally used for recording cortical field potentials, were utilized for bipolar stimulation of the cortical area. A train of brief electrical pulses was delivered to the loci producible of the no-go potential at different times after the onset of go visual stimulus. The stimulation suppressed the go movement by cancelling and delaying. The grade of the suppressor effect depended on the timing of electrical stimulation after the onset of visual stimulus, and was maximal at around the time of appearance of the no-go potential. The suppressor effect was compared with that produced by stimulating some other areas in the prefrontal cortex and the premotor cortex, and was found rather unique in those areas producible of the no-go potential.(ABSTRACT TRUNCATED AT 250 WORDS)