Arterial plasma levels and renal venous overflows of immunoreactive neuropeptide Y (NPY-LI) and calcitonin gene-related peptide (CGRP-LI) were studied during mental stress (a modified version of Stroop's colour word conflict test--CWT) and during i.v. infusions of step-wisely increasing doses of adrenaline (ADR) in 12 healthy male volunteers. At rest, mean arterial plasma levels of NPY-LI and CGRP-LI were 27 +/- 2 pmol l-1 and 61 +/- 9 pmol l-1, respectively. No renal venoarterial concentration difference could be demonstrated for either peptide at rest. Although CWT caused a three-fold increase in the simultaneously measured renal venous overflow of noradrenaline, indicating markedly increased renal sympathetic nerve activity, the arterial levels of NPY-LI were unchanged and the net renal overflow of NPY-LI was only slightly (not significant) and transiently increased. CWT also failed to influence CGRP-LI levels in arterial plasma or CGRP overflow from the kidney. During ADR infusions, which increased arterial plasma ADR from 0.25 +/- 0.06 to 6.43 +/- 0.27 nmol l-1, NPY-LI levels were unaffected but CGRP-LI levels in arterial plasma were elevated (P less than 0.001 by ANOVA). No net renal overflow of CGRP-LI could, however, be demonstrated. These findings suggest that CWT is not powerful enough a stimulus to significantly enhance systemic or renal overflows of NPY-LI even though marked renal sympathetic activation occurs. During ADR infusions plasma CGRP-LI levels increased but renal veno-arterial differences of CGRP-LI were unaltered, indicating that CGRP-LI may be released from sites other than the kidney by ADR.