The water extracts of 82 Korean medicinal herbs were examined for the binding affinity on the recombinant human muscarinic acetylcholine receptor subtype 1 (mAChR-M₁) produced from the CHO (Chinese Hamster Ovary) cell line. Of those tested, the extracts of Coptidis Rhizoma, Phellodendri Cortex, Hedyotis Herba and of Terminariae Fructus were found to exhibit a significant competition with [³H] N-methyl-scopolamine for the specific binding to mAChR-M₁ in a dose dependent manner, respectively.