A review with 29 refs. covering reformulated gasolines and their oxygenated components (alcohols, ethers), production, applications and advantages of MTBE as gasoline component, MTBE toxic properties and (bio)degradability. High octane number, low partial pressure, low atmospheric reactivity and suppression of C6H6, AcH, 1,3-butadiene and VOC emissions from gasoline speak In favor of MTBE as gasoline component. Its toxicity, degradability and cancerogenicity require more studies. So far there Is no safe substitute (ETBE?) for MTBE.