According to the European Pharmacopeia and the United States Pharmacopoeia dimethyl sulfoxide (DMSO) is a class 3 solvent and it is used in pharmaceutical industry amongst others as an additive for the lyophilisation process. DMSO has a very low vapour pressure and is therefore difficult to remove during freeze drying, with the result that a significant part of the applied DMSO remains in the dried product. For toxicological reasons, as well as for transport and storage it is important to know about the amount of residual solvents in the lyophilised products. Hence, there is a need for a validated method for determination of the content of residual DMSO, but none of the Pharmacopeias provides a concise method for this determination. We have worked out a convient method for the determination of DMSO in lyophilised pharmaceuticals by static headspace gas chromatography coupled with mass spectrometry which requires only 25 mg of the sample. The sample is placed in a 20 mL headspace vial and incubated for 20 min with shaking at 350 rpm at 80 °C before analysis. The method is linear in the range of 0.05 - 10.00 mg DMSO, the LOQ was set as the lowest point of the calibration curve, and the mean recovery was 108.5%. This fully validated method was applied for the analysis of lyophilised pharmaceuticals with different starting DMSO amounts (2.75 -22.00 mg).