A mixture of linear and cyclic methylsiloxanes was analysed to characterize the different types of siloxane structures using gas chromatography (GC), mass spectrometry (MS) and Fourier transform infrared (FT-IR) spectroscopy. Siloxane structures are formed by hydrolysis of dimethyldichlorosilane under controlled conditions in technical applications. In the presence of methyltrichlorosilane or even trimethylchlorosilane, linear polydimethylsiloxanes and mono-, bi- or polycyclic methylsiloxanes are synthesized depending on the reaction conditions. The main structural units are (CH3)3SiO1, (CH3)2SiO and (CH3)SiO3. GC-MS may provide molecular mass information, but it is not able to identify isomeric structures, which are also formed in lower quantities by the mentioned reactions. Coupling GC with FT-IR enables the determination of group frequencies to assign specific structures. Thus, combination of GC with MS and FT-IR may be used in elucidating complex cyclosiloxane compounds. FT-IR measurements were performed with a Tracer unit.