The effects of different doses of calcitonin gene-related peptide (CGRP) on passive avoidance behaviour were studied in male rats following its intracerebroventricular (i.c.v.) administration. Treatment with doses of 200 ng, 300 ng, 500 ng or 1 microgram was performed prior to learning, immediately and 6 h after the learning session and 30 min before the 24 h retention test. CGRP enhanced the avoidance latency in a dose-dependent manner at each time studied, with the exception of 6 h after the learning session. It is concluded that CGRP might be able to lengthen the passive avoidance latency by facilitating learning and memory formation.