Potassium channels in human skin fibroblast have been studied as a possible site of Alzheimer disease pathogenesis. Fibroblasts in Alzheimer disease show alterations in signal transduction pathway such as changes in Ca2 homeostasis and/or Ca2-activated kinases, phosphatidylinositol cascade, protein kinase C activity, cAMP levels and absence of specific K channel. However, little is known so far about electrophysiological and pharmacological characteristics of large-conductance Ca2-activated K (BKCa) channel in human fibroblast (CRL-1474). In the present study, we found Iberiotoxin- and TEA-sensitive outward rectifying oscillatory current with whole-cell recordings. Single channel analysis showed large conductance K channels (106 pS of chord conductance at 40 mV in physiological K gradient). The 106 pS channels were activated by membrane potential and [Ca2]i, consistent with the known properties of BKCa channels. BKCa channels in CRL-1474 were positively regulated by adenylate cyclase activator (10μM forskolin), 8-Br-cyclic AMP (300μM) or 8-Br-cyclic GMP (300μM). These results suggest that human skin fibroblasts (CR-1474) have typical BKCa channel and this channel could be modulated by c-AMP and c-GMP. The electrophysiological characteristics of fibroblasts might be used as the diagnostic clues for Alzheimer disease.