This study demonstrates a new approach for converting SO2 into elemental sulfur by adding CH4 in a radio-frequency (RF) plasma reactor. With the applied power (P) of the RF reactor specified at 90 W and operating pressure set at 4000 N/m(2), it was found that as the CH4/SO2 ratio (R) was increased from 0.3 to 1.0, most sulfur-containing products were in the form of elemental sulfur. While R was increased from I to 2, the content of elemental sulfur was decreased significantly, but CS2 was increased dramatically. While R was increased from 2 to 3, both elemental sulfur and CS2 contents became quite comparable. Nevertheless, it was found that both H-2 and CO (that is, syngas) were the main nonsulfur-containing products under all testing conditions. These results indicate that the use of the RF plasma technique was not only beneficial to convert SO2, but also was able to convert CH4 into useful materials. For R = 0 (that is, no CH4 was introduced), it was found that the SO2 conversion (i.e., eta(SO2)) = 0.084, indicating that the RF plasma process was inadequate to convert pure SO2 without adding CH4 as a reducing agent. While R was increased to 2, it was found that mu(SO2) 2 was improved significantly to 0.968 accompanied with eta(CH4) = 0. 999. But as R was increased from 2 to 3, both eta(SO2), and eta(CH4), were slightly decreased Both eta(SO2) and eta(CH4) also were sensitive to the applied power (P). As P was increased from 15 W to 90 W at R = 2, it was found that both eta(SO2) and eta(CH4) were increased dramatically from 0.247 and 0.320 to 0.968 and 0.999, respectively. But as P was increased from 90 W to 120 W, the increase on both eta(SO2) and eta(CH4) became very limited Based on these, this study suggests that the operating condition of R = 2 and P = 90 W would be the most appropriate combination for SO2 conversion. (C) 2004 American Institute of Chemical Engineers.