We recorded single neuronal activities in the anterior cingulate cortex of monkeys while they were performing discriminative pain-avoidance and reward tasks: a prediction cue was presented for 0.5-1.5 s, followed by a red or green discrimination cue (1:1, random) for 1.0 s; painful stimuli were presented if the monkey failed to respond during the red cue; a reward was given, subsequent to a cued 1 s delay, if the monkey responded after the green cue. Among 775 neurons recorded, 196 neurons showed significant activity during one or more observation periods; 36 during the prediction period; 77 during the discrimination period; 41 during the delay period; 85 during the response period; 40 during the pre-reward period; and 15 during the reward-ingestion period. Of 77 neurons activated during the discrimination period, 47 showed exclusive activity either during the red (34) or during the green (13) cue: of 85 neurons activated during the response period, 64 showed exclusive activity either for pain-avoidance (37) or obtaining a reward (27). Control experiments confirmed that the neuronal activity could not be attributed to simple visual or motor processes. The results suggest that some anterior cingulate neurons are involved with anticipation of, and response selection for, imminent events.