Sixteen coals from brown to bituminous coal have been pyrolyzed in high-purity He at 400 K/min up to 1000 degrees C with a fixed bed reactor, and the nitrogen distribution has been examined in detail. Nitrogen mass balances fall within 96-103%. Not only volatile nitrogen (HCN, NH3, and tar) but also N-2 is formed, and among these N-2 is the dominant product for almost all of the coals. Conversion of coal nitrogen to N-2 depends strongly on coal type. A German brown coal gives the highest conversion of approximate to 60%, followed by approximate to 50% from a Chinese lignite. No relationship between N-2 formation and coal rank is observed. As N-2 increases, volatile nitrogen decreases slightly, but char nitrogen decreases remarkably, which means a strong, reverse correlation between N-2 and char nitrogen. When the lignite char devolatilized at 600 degrees C is heated to 1000 degrees C, conversion of the nitrogen to N-2 proceeds almost exclusively. These observations show that N-2 originates mostly from char nitrogen and/or precursors. The mechanism of N-2 formation is discussed mainly in terms of the catalysis of solid phase reactions by Fe-containing minerals in low-rank coals.