Rapid and precise method for the determination of 8-iso-prostaglandin F(2alpha), an essential marker of the oxidative stress, in exhaled breath condensate (EBC) was developed. The protocol consisted of stable isotope dilution, immunoseparation combined with selective and sensitive LC-ESI-MS/MS operated in multiple reaction monitoring (MRM) mode. The imprecision of the developed method was below 8.8%, the parameter of mean inaccuracy was determined as <9.6% (0-250pg of 8-iso-prostaglandin F(2alpha)/ml EBC). The limit of detection (LOD) was 1 pg/ml EBC and limit of quantification (LOQ) 5 pg/ml EBC. A significant difference in 8-iso-prostaglandin F(2alpha) content between the group of asbestosis patients and healthy volunteers was found.