The main aim of the present study was the evaluation of proteins and antioxidant potential in ethylene-treated kiwifruit during the first 10 days of ripening. Kiwifruit samples were randomly divided into two groups: treated and untreated. Flesh firmness, sensory value, visual score, free sugars, soluble solids, ethylene biosynthesis, proteins, dietary fibers, total polyphenols and antioxidant potential were determined in both groups. Ethylene (100 ppm) at 20 degrees C for 24 h was used in the treated group. The flesh firmness and acidity in treated samples decreased significantly in the early stage of ripening simultaneously with significant increase in the contents of free sugars, soluble solids, endogenous ethylene production, sensory value, 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase and ACC oxidase activities, total polyphenols and related antioxidant potential, and was significantly higher than in untreated samples (P < 0.05). Proteins were extracted from kiwifruit and separated by modified sodium dodecyl sulphate polyacrylamide gel electrophoresis. The separation was resolved into 14 protein bands. Some minor quality changes were found only in the 32 kDa band, which was more pronounced in the treated samples. In conclusion, ethylene treatment of kiwifruits leads to positive changes in most of the studied kiwifruit compounds and to an increase in the fruit antioxidant potential. It shortens the ripening time and improves fruit quality by decreasing its flesh firmness and acidity. Some minor changes in the protein profile did not affect the fruit taste and quality.