A high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometric method was useful for the simultaneous determination of aconitine-type alkaloids (jesaconitine, aconitine, mesaconitine, aljesaconitine A, aljesaconitine B, hokbusine A, deoxyjesaconitine, deoxyaconitine, hypaconitine, 14-anisoylaconine, 14-benzoylaconine, and 14-benzoylmesaconine) and other alkaloids (neoline, delcosine, 14-acetyldelcosine, kobusine, pseudokobusine, and lucidusculine found in Aconitum japonicum. These compounds were quite stable under the conditions used, and the protonated molecules or fragment ions characteristic of the molecule appeared as base peaks in the mass spectra and were used for selected ion monitoring. The method is linear over the range from 10 ng (50 ng; jesaconitine and neoline) to 10 μg of alkaloid per injection. The detection limits of aconitine-type alkaloids and neoline were ∼ 2–20 ng per injection.