Abstract: Theab ility fo r DNA repair is an impo rtan t ho st facto r w h ich inf luences the individual su scep t ib ility to geno tox2 ic carcinogen expo su res. It has been show n in differen t case2con t ro l studies that DNA repair capacity (DRC) can be reduced in lung cancer pat ien t s. W e have u sed an alkaline com et assay to m easu re the cellu lar DRC in peri2pheral b lood lymphocytes of lung cancer pat ien t s and tumo r2f ree con t ro l sub ject s. A ddit ionally, fo r fu rther characterisat ion and in o rder to iden t ify DNA repair genes w h ich m igh t be respon sib le fo r tbe ob served impair2 m en t of DNA repair, w e developed a DNA array fo r exp ression analysis of hum an DNA repair genes: PCR f ragm en t s f rom I. M. A. G. E. clones of mo re than 60 know n genes, direct ly o r indirect ly invo lved in DNA re2 pair, have been p repared and u sed fo r array p reparat ion. So far, w e found a stat ist ically sign if ican t associat ion betw een reduced DRC and elevated risk fo r non2sm all cell lung cancer (P < 0. 0001). O u r cellu lar assay enab led u s to reliab ly iden t ify individuals w ith reduced DRC. Fu rthermo re, exp ression analyses w ere perfo rm ed w ith mRNA iso lated f rom individuals show ing either h igh o r low values of cellu lar DRC. The repo rted com et assay resu lt s w ill be discu ssed together w ith the individual differences in exp ression of DNA repair genes.