CaCO3 was impregnated with aq. Na2CO3 and NH4Cl so as to yield 3% Na and 0, 0.5, 1, 2,5 and 10% Cl (based on CaO wt.) Na/CaO-Cl catalysts. Each catalyst was calcined in air at 750degreesC and used immediately in the reaction of a (10:1) CH4/O-2 mixture at 700, 750, 800, or 850degreesC, contact time 0.4 s(.)g/cm(3). The 0% Cl catalyst gave a max. yield of C2+, 10%, at 800 and 850degreesC. The 2% Cl catalyst gave the max. selectivity toward C2+, 90%, at 850degreesC. As % Cl was increased, the conversions of O-2 and CH4 fell. At 2% Cl, the overall selectivity and the selectivity towardC(2)H(6) were max., exceeding those of the 0% Cl catalyst. At 850degreesC, the selectivity toward C3+ was 6%. The selectivity toward C2H6 on the 2% Cl catalyst was enhanced (70% vs. the 52% on 0% Cl) only at 850degreesC. Generally, Cl reduced the activity of Na/CaO catalysts, especially at lower temperatures.