Scutellariae Radix (common name Huangqin), the dried root of Scutellaria baicalensis Georgi, has been frequently used in combination with other herbs in Traditional Chinese medicines for centuries. Our recent study has demonstrated that baicalein, the major flavonoid derived from the herb, stimulates Cl^–secretion across rat colonic mucosa (Ko et al 2002). The present study aims to investigate whether the herbal extract (Chen et al 2000) also stimulates anion secretion in human intestinal T84 cells and the underlying signaling pathways using the short-circuit current (ISC⁾ technique. Data are means ± S.E.M. of n observations.T84 cells were grown on permeable supports for 9 days using standard culture techniques. When clamped in the Ussing chambers and incubated in normal Krebs solution, T84 cells exhibited a basal I_SC of 1.5 ± 0.1 µAcm^-2 and a transepithelial resistance of 627 ± 18 Ωcm²(n = 211). Apical addition of Scutellariae Radix extract (SRE) elicited a concentration-dependent increase in Iwith an EC₅₀ of SC 1.75 ± 0.16 mg/ml. Removal of extracellular Cl^–(n = 4) or basolateral addition of bumetanide (100 µM, n = 6) abolished the I_SC responses. The SRE-induced I_SC responses were sensitive to apical application of different Cl^–channel blockers such as DPC (100 µM), DIDS (100 µM) and glibenclamide (300 µM). The Clsecretory response to saturating concentration of forskolin (10 µM) was not further enhanced by SRE (n = 6). On the other hand, pre-treating the epithelia with the calcium mobilizing agent, thapsigargin (1 µM), did not prevent further increase in I_SC by SRE (n = 5). In contrary, the thapsigargin-evoked IwasSC potentiated by pre-treating the epithelia with SRE (n = 5). Moreover, SRE evoked an increase in cAMP production (n = 5). The SRE-evoked I_SC was sensitive to H89 (5 µM, n = 6), a protein kinase A (PKA) inhibitor and MDL 12330A (10 µM, n = 5), an adenylate cyclase inhibitor. In summary, the results indicate an increase in I_SC by SRE in T84 cells, which is due to Cl^–secretion. These data suggest that activation of adenylate cyclase, cAMP ’elevation and PKA pathway are involved in SRE s secretory action in T84 cells.