Quantification of total N-nitroso compounds (NOC) in urine and gastric juice is achieved by combining photolytic denitrosation with thermal energy analysis. The minimum mass detection limit of the technique is about 10 pmole No. Urine samples with NOC concentration as low as 200 nmolL−1can be analyzed with a precision of approximately 5-10%. The minimum concentration detection limit for gastric juice samples is about 1 μmolL−1. Except for nitrite, no interference is observed from nitrogenous compounds present in urine and gastric juice. The nitrite interference is effectively eliminated with sulphamic acid.