Examined the effects of chronic thalamic lesions on pain reactivity in male rats. Ss underwent acute pain tests through paw pressure, hot-plate, and tail-flick testing, and formalin injection. Ss were subjected to either subtotal, lateral, or medial thalamic lesions produced through electrical current, with reactions to nociceptive stimuli assessed 1-2 mo subsequently. Results show that all types of examined lesions produced significant and persistent decreases in the latencies of the acute mechanical and thermal nociceptive stimuli and increases in pain scores. Findings suggest an important role of the thalamus in pain modulation in addition to that of nociceptive transmission.