An investigation was conducted in Plectranthus forskholii by giving it different concentrations (10, 15, 20, 25, and 30 mgL^-1) of hexaconazole, a fungicide cum plant-growth regulator, in order to find out its effects on growth, pigment composition, and antioxidant potential. The treatments were given as soil drenching on different growth stages. All the concentrations of hexaconazole used significantly decreased the stem length and leaf area, whereas side branches, fresh and dry matter content, photosynthetic pigments, and antioxidant potential were increased. The number of tubers, length and girth of tubers, fresh and dry weight of tubers and tuber pigments were found to be the highest at a 25 mgL^-1 concentration of hexaconazole. Hexaconazole application at 25 mgL^-1 concentration was found to be more effective than 10, 15, 20, 25, and 30 mgL^-1 in promoting fresh and dry weight of root tuber over 165 days after planting. The pigments like chlorophyll, carotenoid; anthocyanins, xanthophylls and antioxidants such as ascorbic acid, reduced glutathione and total phenol were significantly increased under hexaconazole treatment when compared to untreated control plants. To cite this article: G.M.A. Lakshmanan et al., C. R. Biologies 330 (2007).