Irradiation of the flagellate Euglena gracilis by UV-B radiation resulted in inhibition of photosynthesis and motility. After 2 h of UV-B radiation (1.2 W m^-2) the rates of photosynthesis did not completely recover until after 24 h in visible light. After 24 h in darkness the rate of photosynthesis was lower but the recovery time in darkness after UV-B radiation was about the same as in the visible light. In the presence of lincomycin, inhibitor of chloroplast protein synthesis, the recovery of photoinhibiton was totally blocked for up to 16 h recovery in visible light. However, after 24 h recovery in visible light together with lincomycin, photosynthesis was partially recovered but recovery in darkness together with lincomycin did not give any reparation at al1 of photosynthesis. The inhibition of motility had a slower recovery phase and had not fully recovered even after 72 h in visible light.