The near ultraviolet absorption spectrum of chlorine nitrite (C1ONO) has been quantitatively investigated over the wavelength range 230--400 nm at 231 ¿K. An absorption maximum was observed at 290 nm with a cross section of 1.5¿10-18 cm2. The calculated lifetime against photodissociation for ClONO in the atmosphere is 2 to 3 minutes. The large photolysis rate indicates that ClONO does not play a significant role in the stratosphere as a temporary holding tank for chlorine.