The total nitrogen (TN) and water-soluble nitrogenous ions were determined by using CHN Elemental Analyzer and ion chromatography method, respectively, from November 24, 1998 to February 12, 1999 in Beijing. The average concentrations of TN, NH(4) (+) and NO(3) (-) were 10.62 microg N m(-3), 6.67 microg m(-3) and 10.01 microg m(-3), respectively. The total inorganic nitrogen (IN) calculated from NH(4) (+) and NO(3) (-) was 7.45 microg N m(-3), accounting for 70% of TN, i.e., 30% of TN existed as organic nitrogen form (ON). The correlation between ON and other pollution tracers showed that, coal combustion, biomass burning, soil humic matter and secondary formation were the important sources of ON in particulate matter in Beijing.