In order to enhance the quality of producer gas obtained from the biomass gasification process without the use of oxygen, high temperature air-steam gasification may be an advantageous technology. A highly preheated agent (air and steam) can provide additional energy into the process that improves thermal decomposition of the gasified biomass feedstock, and promotes endothermic reactions. In this investigation, the high temperature air-stream gasification process was performed on a fixed-bed downdraft biomass gasifier. The results showed that increasing the gasifying agent preheat temperature led to increased concentrations of H-2 and CO and decreased contaminated tar in the producer gas. Increasing the equivalence ratio resulted in decreased H-2 and CO concentrations and also reduced tar content. The introduction of steam increased gas quality, but excessive steam degraded gas quality. The increased higher heating value of the gasified gas varied between 4.15 and 6.21 MJ/Nm(3).