Studies on the origin of the afferent acetylcholinesterase-containing fibres of the nucleus accumbens in the brain stem of 27 rats were carried out by retrograde fluorescent labeling combined with AChE histochemistry. DAPI or Pr was injected into the nucleus accumbens. The animals survived for 2.5-3 days. DFP was injected intramuscularly 6 to 8 hours before left intraventricular perfusion by 10％ formalin-containing phosphate buffer solution (0.1mol/L, pH 7.4). The frozen serial transverse sections of the brain stem were incubated in Karnovsky-Roots solution. The fluorescent retrograde labeled cells with AChE reaction-positive products were traced under OLYMPUS fluorescence microscope and light microscope simultaneously. The results were as follows: (1) On the ipsilateral side, the retrograde fluorescent labeled cells with AChE reaction-positive products were found in the following nuclei: area ventralis tegmentalis (AVT), substantia nigra (SN), nucleus raphes mesencephali caudalis(cmr), nucleus tegmenti pedunculopontinus(tpt), nucleus raphe dorsalis(dr), nucleus centralis superior (cs), nucleus reticularis tegmenti pontis(rtp), Locus ceruleus (Lc), nucleus tractus solitarus(tsol), nucleus raphe pallidus (rpa), nucleus reticularis paramedianus (rpm), subnucleus reticularis ventralis(rv), nucleus reticularis lateralis(rL). (2) On the contralateral side, a few of the above mentnioned cells were also found in AVT, SN, dr, cs, and tsol.