Electrospray ionization (ESI) tandem mass spectrometry collision-induced dissociation (CID) fragmentation processes of a series of nitroaromatic, nitramine and nitrate ester explosives were studied in the negative-ion mode using daughter-ion, parent-ion and neutral loss scans. 2,4,6-Trinitrotoluene (TNT) was characterized by loss of OH, NO and NO2. 1,3,5-Trinitro-1,3,5-triazacyclohexane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) were characterized by loss of CH2NNO2, NNO2, NO2 and N2O. 2,4,6,N-Tetranitro-N-methylaniline (tetryl) and its hydrolysis product, N-methylpicramide, showed losses of NO2, HNO2 and NNO2. Pentaerythritol tetranitrate (PETN), glycerol trinitrate (nitroglycerin) and ethylene glycol dinitrate (EGDN) were characterized by loss of CH2NO2, CH2NO, CHNO2, ONO2, NO2 and NO. Similarities were found between ESI and negative chemical ionization mass spectra as well as between their CID fragmentation processes. Detection limits of TNT, tetryl, PETN, RDX and HM were found to be in the 5–10 pg range. © 1997 John Wiley & Sons, Ltd.