The aim of this thesis was the development of a multi-residue method for the simultaneous determination of various organic contaminants in water by GC / MS. Substances from 9 different classes of compounds were investigated: Aniline, chlorobenzenes, cresols, musks, polybrominated biphenyls, polybrominated diphenyl ethers, polychlorinated biphenyls, phenols, and softeners. According to preliminary tests, the liquid-liquid extraction was chosen for the enrichment of the analytes and further optimized. To increase the sensitivity of the phenols, part of the extract is derivatized with BSA (N,O-bis(Trimethylsilyl)acetamid), prior to the measurement. To ensure the reliability and suitability of the developed method, a validation was performed based on the specifications of DIN 31546. For this purpose, the linear working range, limits of quantification, average recovery and the relative standard deviation were determined. The specificity of the method is secured by the retention time and the characteristic ions. The limits of quantification of PCBs, BDEs, PBBs and musk compounds are in the range 0.05 to 0.25 g/l. The limits of quantification of anilines, chlorinated benzenes, phenols and plasticizers are between 0.1 - 1 g/l. Overall, in this thesis a multi-method was developed, which enables to determine 105 contaminants simultaneously. By means of a simple and rapid sample preparation followed by GC / MS measurement substances from nine different classes of compounds can be qualified and quantified.