Mallee bark (75-150 mu m) was pyrolyzed at 400-900 degrees C under various conditions to investigate chlorine (Cl) release and distribution among char, tar, and gas. All Cl species in the bark are in form of water-soluble chlorides. In a fixed-bed pyrolysis reactor, the release of Cl is insensitive to pyrolysis temperature between 400 and 900 degrees C, with Cl completely released with volatiles (similar to 77% in tar and similar to 23% in gas). In a drop-tube/fixed-bed reactor, under continuous feeding, the amount of Cl released at 400 degrees C is similar to that in the fixed-bed reactor. However, Cl retention in char increases with temperature, reaching a maximum at 600 degrees C (similar to 42%), and then decreases with further temperature increases (e.g., only similar to 6% at 900 degrees C). In the same drop-tube/fixed-bed reactor under pulsed feeding conditions, Cl release and distribution follow similar trends but to a lesser extent. The results confirm that volatile char interactions also play important roles in Cl release and distribution among products during biomass pyrolysis and that Cl in char is thermally unstable at elevated temperatures. Calculations by difference further suggest that substantial Cl (47-84%) is present in tars. Quantification of Cl in tar was then carried out experimentally via in situ combustion of biomass volatiles produced using a two-column pyrolysis/combustion reactor. The results confirm the presence of substantial organically bounded Cl in tar. The mass balances of Cl in char, tar, and gas achieve similar to 100% closure during biomass pyrolysis in the fixed-bed reactor between 400 and 900 degrees C, as well as that during biomass pyrolysis in the drop-tube/fixed-bed reactor below 600 degrees C. However, at temperatures >600 degrees C, 100% Cl mass balance cannot be achieved during in situ combustion of volatiles and the data suggest that some Cl react with inorganic species (e.g., Na and K) in the gaseous phase to form alkali chlorides, which are deposited on the reactor wall.