Pulsed, turbulent jet diffusion flames were examined experimentally in both microgravity and normal gravity. In all cases the flames were fully-modulated, that is, the fuel flow was completely shut off between pulses. Unheated ethylene fuel was injected using a 2 mm diameter nozzle into a combustor with an oxidizer co-flow at one atmosphere pressure. Microgravity conditions (10-4g) were achieved for 2.2 s in drop tower tests. The ensemble-averaged flame length of fully-modulated flames consisting of isolated, compact puffs (injection times less than approximately 40 ms) does not appear to be strongly impacted by buoyancy. The most marked increase in flame length due to the removal of buoyancy in microgravity occurs for flames with short injection times and high duty cycle. A smaller increase in flame length is seen for flames with elongated structures (injection times of up to 300 ms) and for steady-state flames. The changes in flame length with injection duty cycle can be partly attributed to the duty cycle at the flame tip being significantly greater than that at injection. © 2002 by the authors.