A method was developed for the determination of human hemoglobin (Hb) adducts from hexahydrophthalic anhydride (HHPA) and methylhexahydrophthalic anhydride (MHHPA). The procedure includes lysis of erythrocytes, dialysis of the Hb-solution followed by acid hydrolysis. The released hexahydrophthalic (HHP) acid and methylhexahydrophthalic (MHHP) acid were purified using a combined liquid-liquid and solid-phase extraction procedure followed by derivatization with pentafluorobenzyl bromide. The derivatives were analyzed using GC-MS in negative ion chemical ionization mode with ammonia as moderating gas. As internal standards, deuterium-labeled HHP and MHHP acids were used. The detection limits were 0.3 pmol/g Hb for HHP acid and 0.9 pmol/g Hb for MHHP acid. The between-day precisions for HHP acid were 18% at 2 pmol/g Hb and 10% at 13 pmol/g Hb. For MHHP acid, the precision was 27% at 2 pmol/g Hb and 14% at 22 pmol/g Hb. The method was applicable for analysis of Hb adducts from workers occupationally exposed to HHPA and MHHPA.