The shape of mild fires is a fundamental consideration when developing a lighting technique for controlled burning. The study reported in this paper was undertaken to see whether further improvements could be made in a method of lighting commonly employed in the jarrah forest of Western Australia. Under this method lighting-lines are oriented across the wind, and spot fires are placed along the line at intervals of half the width between the lines. The average shape in these investigations, expressed as the ratio of the rate of spread of the flank fire to the rate of forward spread of the head fire, was 0.5. Rates of spread of the headfire, flankfire and backfire are presented diagrammatically for fires with forward spreads ranging from 1 to 4 feet per minute. The variation in average shape fires with rate of spread within this range was found to be insufficient to warrant a change in the present method of lighting. © Institute of Foresters of Australia. Abstract reproduced by permission.