The involvement of the NMDA and non-NMDA receptors in the task-related neuronal activity of the primary motor cortex (MI), premotor cortex (PM), supplementary motor area (SMA), and an area rostral to the SMA (pre-SMA) of two monkeys (Macace fuscata) was examined during performance of a trained motor task. The selective NMDA antagonist 0-2-amino-5-phosphonovaleric acid (APV) and the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were iontophoretically applied to motor task-related neurons. A total of 568 task-related neurons (435 movement related, 83 set related, 50 mixed type) were recorded from the MI, PM, SMA, and pre-SMA, and the effects of APV and CNQX were examined in the individual neurons. In many neurons, APV selectively or preferentially suppressed the spontaneous discharge rather than movement-related activity. In many neurons, the movement-related activity was more selectively or effectively suppressed by CNQX than by APV. However, the set-related activity was affected by both APV end CNQX. The neurons in layers I and II were affected more strongly by APV end CNQX than those in layers V and VI. No correlation was found between the magnitude of task-related activity in the control (no drug application) period and the effectiveness of APV or CNOX. These results indicate that both NMDA and non-NMDA glutamate receptors are involved in motor task-related neuronal activity of both primary and secondary motor areas, although the contribution of these two receptors to individual neuronal activity varies a great deal.