A total of 47 beer samples, produced in Korea. Were analyzed for their N-nitrosamine levels by gas chromatography-thermal energy analyzer. N-nitrosodimethyamine(NDMA) was detected in 35 of 47 sam-ples analyzed. The range of levels was 0~7.2$mu extrm{g}$/kg while the average was about 0.9mg/kg. The identity of NDMA was confirmed by mass spectrometry. Samples which were found only NDMA before nitrosation were detected to include N-nitrosopyrroidine(45$mu extrm{g}$.kg) and N-nitrosomorpholine(4$mu extrm{g}$/kg) as well as NDMA(837$mu extrm{g}$/kg)