Newcomers to the field will find this book indispensable. Experts, such as organic mass spectrometrists in the chemical, pharmaceutical, and petrochemical industries, will find it a valuable time-saver in interpreting the spectrum of an unfamiliar compound when information is lacking on the history of the sample. This volume is an invaluable resource for interpreting the copious spectral data generated in gas chromatography and mass spectrometry investigations. Comprehensive tables show the most probable assignments for peaks in electron ionization mass spectra of organic compounds. This expanded edition lists more than 3000 structures corresponding to 1500 elemental compositions, several times the number in the first edition of this book published in 1963.