We have measured the shape of the luminous zone in a laminar jet diffusion flame burning methane, ethylene, and propane in quiescent air in the pressure range 0.02-0.1 MPa. Soot emission by the flame was not permitted. The flame became more slender and luminous as the pressure increased. At relatively high fuel flow rates, the ethylene and propane flame heights increased with pressure. At low fuel flow rate, the flame height decreased as pressure increased for all three fuels. At high fuel flow rate, the methane flame height first decreased and then increased with pressure, due to the low tendency of methane to form soot. Finally, we observed a tendency toward decreasing - increasing - decreasing flame height at certain fuel flow rates and in certain pressure ranges.