This document specifies a method for determining µ caprolactam and É laurolactam in polyamides by gas chromatography. It is applicable particularly to the determination of µ caprolactam in polyamide 6 and É laurolactam in polyamide 12. Two variants of the basic method are specified: Method A is an extraction method with boiling methanol, and the extract is injected into a gas chromatograph. Method B is a method using a solvent, and the solution is injected into a gas chromatograph.