The effect of meditation on pain perception was investigated. Zen meditators and controls were instructed to attend, in different ways, to painful and non-painful thermal stimuli. Conditions included: a) baseline, b) concentration: attend exclusively to the left calf, c) mindfulness: attend to the left calf and observe, moment to moment, in a non-judgmental manner. Meditators required higher temperatures to elicit pain (50°C vs 48°C). In meditators stimulus intensity ratings were lowered during mindfulness while controls did not differ from baseline. The number of hours of meditative training correlated with the size of the analgesic effect of mindfulness. During concentration intensity and unpleasantness ratings increased for controls whereas meditators showed a slight decline. Meditators also had a stronger tendency to observe their own experience and be non-reactive as measured by a trait mindfulness scale. These results suggest that Zen meditation has both long and short term effects on pain perception.