Outside the central nervous system, calcitonin-gene-related peptide (CGRP) plays an important role in the control of regional blood flow. The present authors studied the renal haemodynamic effects of CGRP in the model of isolated perfused rat kidney (IPRK). This experimental model avoids the complex feed-back mechanisms activated by any modification of renal perfusion pressure. It was found that the infusion of CGRP in the IPRK induced a marked decrease of perfusion pressure; this vasoactive effect is well measured by the glomerular morphometric analysis that shows a striking increase in the glomerular diameter and volume.