The pedunculopontine tegmental nucleus (PPTN) is the major source of cholinergic projections in the midbrain and also contains non-cholinergic (GABAergic, glutamatergic) neurons. Classical literature emphasizes that the tonic activity of PPTN neurons plays a role in controlling the sleep/wake state and are important for regulating the activation state of the thalamus via their cholinergic projections. In slice preparations, PPTN neurons exhibit a slow tonic repetitive firing pattern in the beta/gamma band range when maximally activated. Recently, periodic activity was recorded from the PPTN of patients with Parkinson's disease who were treated with levodopa, suggesting that periodic firing is a feature of the functioning PPTN and plays a role in general movement control. However, it remains unclear whether PPTN neurons exhibit periodic firing patterns during various behaving conditions, including executing conditioned behaviors, seeking reward, or during resting. To address this question, we recorded the activity of single PPTN neurons in monkeys during visually guided saccade tasks, and analyzed their firing patterns. One population of PPTN neurons exhibited a regular firing pattern in that the coefficient of variation of interspike intervals was lower than that of theoretical random and irregular spike trains. Furthermore, one group of PPTN neurons exhibited a clear periodicity of firing. Many of these neurons exhibited a periodic firing pattern during highly active states, either during the task execution period or intertrial interval. The periodic firing neurons exhibited longer action potential durations and were also mainly distributed in the caudal part of the PPTN, consistent with the reported feature of cholinergic neurons. These task context-related changes in periodic discharge of PPTN neurons might regulate the monkey's motivational and arousal level to perform the task.