The antioxidant effect of 5-Aminosalicylic acid (5-ASA) on copper-mediated LDL oxidation was followed either by the emitted chemiluminiscence (CL) or by UV-vis spectroscopy. 5-ASA addition extends the lag phase in a concentration-dependent manner without changes in the rate of the process in the autoaccelerated phase. The antioxidant behavior of 5-ASA was very similar to that of Trolox, a very efficient water soluble antioxidant. The copper-binding capacity of 5-ASA was evaluated by UV-visible spectroscopy. The addition of copper to a 5-ASA solution increases the absorbance at 332 nm and generates a new band at 298 nm. These changes in the UV-vis spectra indicate formation of a complex between 5-ASA and copper. However, LDL protection by 5-ASA is unrelated to its copper chelating capacity