Several developments have been made in mass spectrometry during the last few years. One of the most significant developments, fast-atom bombardment mass spectrometry, has tremendous potential for the characterization of lubricants. The technique is described, and examples of its use for the direct, rapid, and semiquantitative characterization of synthetic base oils and additives in lubricants are given.Presented at the 40th Annual Meeting in Las Vegas, Nevada May 6–9, 1985