Abstract Based on a method for trapping direct-alkylating intermediates with scavenger reagents possessing a nucleophilic side-chain and an N-nitroso group as a marker, a sensitive test system for the detection of N-nitrosamides and related compounds has been developed. N-Nitroso- N- tert-butylglycine is an effective scavenger reagent for this purpose. It reacts readily with diazoalkanes released from N-nitrosamides on treatment with alkali to form the corresponding esters which are analysed by gas-liquid chromatography using a thermal energy analyser. The method is easy to perform and specific for N-nitroso compounds that decompose to non-polar diazoalkanes on treatment with alkali. A determination limit of 2 ng solids/sample was established for methylated NTBG formed from N-methyl- N-nitro-sourea following treatment with alkali.