Abstract Electron-impact mass spectral fragmentation patterns are reported for various aminothieno-pyridines (TPNH 2) and aeylaminothtenopyridines. The molecular ion TPNH 2+ shows loss of atomic hydrogen, hydrogen cyanide and both thioformyl radical and cation. TPNH 2+ is the most abundant ion in the spectrum of each acylamino compound investigated. A semiquanti-tative mass spectrum of the amine TPNH 2 can be obtained by ...