Using hydrogen and liquid petroleum gas, diffusion flames from an internal mixing nozzle, I.M.N., have been investigated experimentally and compared with those from a circular tube nozzle, C.T.N. When compared with C.T.N. flames, the I.M.N. flame length is shorter, the ignition distance is reduced, the blow-off velocity is higher and the flame is more stable on the whole. The chemical species distribution within the flames from both I.M.N. and C.T.N. has been analyzed. The results of the chemical analysis are discussed, considering what would be expected from our earlier fluid dynamical investigations. Improvement of the flame characteristics results from the intense turbulence within the jets just after ejection from the I.M.N. port. This intense turbulence is generated within the mixing chamber of the I.M.N., which promotes the transfer properties between the flame jet and the ambient air.