The nitrogen isotope composition of free glycine (delta N-15(F-Gly)) in atmospheric particulates from different sources was measured to explore whether delta N-15(F-Gly) could be used to indicate the sources of particulates. We found that the delta N-15(F-Gly) released by biomass combustion (range: +16.9 to +27.3 parts per thousand) was significantly higher than that from natural sources (up to 21.6 parts per thousand). The concentration of free Gly in particulates released from fossil fuel combustion (bituminite combustion and vehicle emission) was very low. These results provided the possibility for using the delta N-15(F-Gly), values in aerosol to distinguish biomass combustion from natural sources. In the field, a high correlation between the free Gly concentrations in aerosol and nonsea salt potassium (nss-K+) was observed. The delta N-15(F-Gly) values showed the same temporal pattern with fire points and a link between the delta N-15(F-Gly), values and nss-K+ levels was found. These results suggested that the delta N-15(F-Gly) value in aerosol might be a good indicator for biomass burning.