Wogonin, derived from the root of Scutellaria baicalensis, is a popular herb for its anticancer, anti-inflammatory, neuroprotective and anti-convulsant effects. The purpose of this study was to investigate the effect of wogonin on human hepatic cytochrome P450s (CYP450s) in vitro. Isoform-specific substrate probes of CYP1A2, 2C9, 2C19, 2D6, 2E1 and 3A4 were incubated in human liver microsomes with or without wogonin. IC(50) and K (i) values were estimated and the types of inhibition were determined. Wogonin was a potent, competitive inhibitor of CYP1A2 (K (i) = 0.24 μM), and a weak inhibitor of CYP2C19 (IC(50) = 101.10 μM), but was not able to inhibit CYP2C9, CYP2D6, CYP2E1 and CYP3A4 (IC(50) > 200 μM). Wogonin could inhibit the activity of CYP1A2 and CYP2C19 with varying potency, while it is a strong inhibitor of CYP1A2. These findings suggested that it was necessary to study the potential pharmacokinetic drug interaction in vivo.