An ESI MS/MS library of 800 compounds has been developed and a collection of data is now available for Analyst 1.4 and higher. Compounds include forensically important drugs, such as illegal drugs, some deuterated analogues, hypnotics, amphetamines, benzodiazepines, neuroleptics, antidepressants and many others. For setting up the library of product ion spectra, 20-200 ng of the compounds have been injected either by flow injection or via a short LC-column, the precursor ions were chosen from the Q1 scan spectra, and product ion spectra were generated by CID in the collision cell using three different collision energies (20, 35 and 50 eV). Three spectra of each compound have been collected and compound names, CAS numbers, formulas and molecular weights have been added in the database, which has been generated by the Analyst software. The library can be used for compound identification during general unknown screening analysis by combination of Q1 scan techniques and subsequent MS/MS analysis in a second analytical run. Quantitative procedures for multi drug analysis using Multiple Reaction Monitoring can be established by selection of product ions and suitable collision energies from the library. For publication of the spectra, PDF-files have been generated and can be viewed on-line as supplementary data or from the website in alphabetical order: (supplementary data, should be made available via ELSEVIER-WEBSITE or via ).