A method is described for the determination of volatile organic acids in the atmosphere, motor exhausts, and engine oils. Atmospheric organic acids were collected on a KOH impregnated quartz filter and derivatized to rho-bromophenacyl esters. The derivatives were analyzed by high-resolution capillary gas chromatography and gas chromatography-mass spectrometry. C1-C10 aliphatic organic acids and benzoic acid were detected in Los Angeles air. Acetic and formic acids are dominant followed by propianic acids. Total concentrations measured were 0.37-7.45 ppb. Organic acids (C1-C10) were also detected in the motor exhaust from a single automobile at idle conditions and showed that the distribution of individual acids was similar to that in the air, but the concentration was 17 times higher than for the average atmospheric content. Formic, acetic, and benzoic acids were detected as major species of used engine oil, but their content is negligible in new oil.