The aim of the present study was to investigate rapid effects of aldosterone and other steroids on intracellular pH of vascular smooth muscle cells and to compare these effects with those of peptide hormones. After addition of 100 nmol/L aldosterone, initial acidification is followed by significant alkalinisation occurring within two minutes, while 1 mumol/L hydrocortison does not affect intracellular pH. The initial response to 100 nmol/L angiotensin II is similar; however, subsequent alkalinization is not seen for this agonist. PDGF induces an initial acidification followed by a minor recovery so that cells remain acidified for eight minutes. Both pH recovery after angiotensin II and alkalinization after aldosterone were blocked in sodium-free medium. These results demonstrate rapid effects of aldosterone on intracellular pH in vascular smooth muscle cells, which include final alkalinization not seen after angiotensin II or PDGF.