ABSTRACT Prunes, obtained by drying certain cultivars of plums, have greater antioxidant activity than most other fruits and vegetables. Recent research has attributed only a minor part of this antioxidant activity to phenolic compounds, and it has been hypothesized that most of the antioxidant activity is caused by unknown or new products created during processing. In this study, the relationship between the antioxidant properties of prunes and their phenolic compound and brown products content has been investigated. The latter is a result of the nonenzymatic browning reaction. The results show that most of the antioxidant activity of fresh plums is caused by the polyphenolic fraction. The prunes, obtained by drying at 60 and 85C, despite the significant decrease in polyphenols, showed an increase in antioxidant activity. This was mostly because of the nonenzymatic browning reaction products, mostly low molecular weight compounds, whereas polyphenols contributed only to 23% of the total value. PRACTICAL APPLICATIONS Results of this research could have direct or indirect applications. First of all, results give evidence of the best drying conditions related to the nutritional profile of the prunes. Results related to the antioxidant activity of melanoidin compounds can, moreover, stimulate medical researcher to test if melanoidin extracts are really in vivo or ex vivo antioxidants, and in that case, producers of functional foods or food ingredients can be encouraged to try to isolate and characterize the compounds responsible for increased antioxidant activity.