The authors examined the possible interactions of some nonsteroidal anti-inflammatory drugs with hydroxyl radicals by means of the test based on degradation of 2-deoxy-D-ribose initiated by hydroxyl radicals. The method is based on spectrophotometric measurement of thiobarbituric acid (TBA)-reactive carbonyl compounds that are formed in the degradation reaction of 2-deoxy-D-ribose by hydroxyl radicals (HO*) generated in the Fenton-reaction between iron(II)-ions and hydrogen peroxide (H2O2). The authors studied the degradation-inhibitory effect of phenacetin, paracetamol (acetaminophen), indomethacin, ibuprofen, diclofenac sodium, salicylic acid and salicylamide used in 100 microM and 200 microM concentrations, in the present or without addition of EDTA. In the short term (10 minute) studies paracetamol and salicylic acid proved to show the most effective degradation inhibitory effect. In the longer-time (120 minute) studies after the early inhibitory effect of paracetamol, indometacine and salicylic acid, an increase of the TBA-reactive compounds could be observed.