Peripheral OKN was produced by stimulating the visual field with a special device, designed by Miyoshi et al. Stimuli to induce peripheral OKN and rotatory nystagmus (RN) were applied to the same subject simultaneously. The results obtained were as follows. 1) In the case of the whole visual field, with a target velocity of 30 degrees/sec the combined slow-phase velocity of OKN and RN was also a constant 30 degrees/s in any phase of rotation of the subject and with any combinations of the rotationary directions of subject and target. 2) In the case of the peripheral visual field; when both OKN and RN were in the same direction, the slow-phase velocity of the combined OKN was 10-20% greater than that of the peripheral OKN alone. However, the combined OKN never exceeded the velocity of the target. In contrast, when OKN and RN directions were opposed, combined OKN was correspondingly decreased by about the same 10-20% amount.