Considerable research has been conducted in the past 20 years to advance gasification technology and adapt this technology for biomass applications. The gasification process itself is relatively well developed, and producer gas can be generated at fairly large scales from a variety of feedstocks. The largest impediments now facing the application of biomass gasification for energy production are the inabilities of the current ancillary systems to allow for economical production of a clean producer gas, free of contaminants. Ancillary systems are operations other than the actual gasification process and generally fall into two categories: fuel preparation and feeding of the feedstock (prior to gasification) and gas-cleaning systems (subsequent to gasification). Fuel preparation systems ensure proper feeding of biomass into a gasification vessel and the obtainment of good-quality gas, while gas-cleaning systems remove contaminants from the producer gas to allow reliable and efficient operation of internal combustion engines, gas turbines, or fuel cells. These ancillary systems, particularly the fuel preparation and feeding systems, generally designed specifically for a single gasification system, are often not mentioned when gasification systems are discussed. This paper attempts to collect this information together for a better understanding of overall gasification systems.