Calcitonin gene-related peptide (CGRP) was applied by iontophoresis onto physiologically characterized neurons. CGRP (20-100 nA) activated both wide-dynamic-range (5/8) and low-threshold mechanoreceptive units (3/12), but had no effect on nociceptive-specific neurons (0/4). The excitation was of slow onset (30 s to 3 min) and prolonged duration (up to 10 min). In none of the tested units did CGRP cause inhibition. The slow and prolonged action suggests a neuromodulatory role for CGRP in spinal cord sensory processes.