The Federal Aviation Administration FAA Technical Center has performed extensive research toward finding an unleaded replacement for the current leaded aviation gasoline for general aviation aircraft. Described in the report are testing procedures, results to date, and future testing plans. The tests include vapor lock behavior, performance, endurance, detonation analysis, material compatibility, storage stability, volatility, emissions, water miscibility, and flight testing. The volatility tests include Reid Vapor Pressure, distillation, and vapor to liquid ratio tests. The endurance tests involved periodic checks of cylinder wear, particularly valve seat wear, leak downs to determine cylinder compression loss, and oil analysis.