Methods available for measuring hydrocarbons in diesel exhaust were evaluated by the CRC-APRAC Program Group on Diesel Exhaust Composition during 1967-1970. Early tests showed distressingly large variations from instrument to instrument and undesirably large variations among repeated measurements by one instrument. Instrument quality and operator competence were better in later tests and agreement among instruments was relatively good and errors within instruments were small. Current techniques appear acceptable for engineering measurements. No further cooperative work is planned by CRC at present, but techniques for measuring hydrocarbons in diesel exhaust will be reappraised periodically.