The identification of aroma compounds, formed from the model reactions of L-ascorbic acid and L-cysteine with or without urea at two different initial pH values (5.0, 8.0) and 140?癈 for 2h, was performed using a solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) technique. The effect of urea on aroma compounds was investigated. 47 aroma compounds were identified. The results showed that sulfur-containing compounds such as alicyclic S compounds, thiophenes and thienothiophenes were the most abundant compounds. Other compounds identified were furans, thiazoles and pyrazines. The addition of urea into the reaction mixture in general caused a reduction or disappearance in content of some sulfur-containing compounds at pH8.0, but caused a increase at pH5.0. On the other hand, it facilitated the generation of several nitrogen-containing volatiles such as pyrazine, methylpyrazine, ethylpyrazine, 2,6-dimethylpyrazine and other alkyl pyrazines which are known to elicit roasty and nutty flavor notes at pH8.0. A plausible explanation for this phenomenon is that ammonia can be released from urea upon heating and the formed ammonia competes with hydrogen sulfide to react with Maillard reaction precursors to produce nitrogen-containing compounds such as alkylpyrazines.