This book presents a library of mass spectra of 1,725 biologically and environmentally important organic compounds, in the form of their trimethylsilyl derivatives (TMS), as well as their linear temperature programmed chromatographic retention indices, RI, whose values are in the range of 700-4700 index units. Of the compounds presented, more than 60% of compounds have not previously been characterized by their mass spectra, and more than 70% not previously been characterized by their RI values. Some of these compounds, never before analysed via MS and GC, were detected by the author’s team in plant tissues.