In this paper we report the effect of the near UV radiation on the flavonoid content of the Ononis spinosa L., during the vegetative phase of its life cycle. Two different features were observed: the increase of the total amount of flavonoids (due to the exposure to the UV-A radiation), and a relative change in the amount of Apigenin and Quercetol. At the same time, we noticed, e.g. the irradiated samples presented always superior weights and sizes, comparing with the controls (at the first phases of growth). The irradiated samples reached lower weights and sizes during the final growth phases. The total amount of the flavonoids increased in a continuous, regular manner. At the same time we observed a progressive increase in the Apigenin content, and a decrease in the Quercetol's content