A rapid, selective and sensitive method for simultaneous determination of acetylcholine and choline in the rat hippocampus was developed. Hippocampus samples with an internal standard were deproteinized with perchloric acid. After homogenization, centrifugation and filtration, the supernatant was directly injected into an isocratic HPLC system with electrochemical detection and a post-column enzyme reactor. The response to the detected substances was linear in the range 0.15 - 30 ng/10 l. Total recovery of the method was higher than 90 %. The method was used for the determination of acetylcholine in the hippocampus of rats poisoned with Soman and treated with a combination of atropine and an oxime (obidoxime or oxime HI-6).