The radiative effect of Pinatubo sulfate aerosol and ash particles on the O2 and O3 photolysis rates in the tropics and the effect of these photolysis rate changes on stratospheric ozone are examined. The impact of volcanic ash particles on the JO2 and JO3 ranges from negligible to significant, dependent on the relative ash content specified. However, regardless of the magnitude of the ash effect on the photolysis rates, the total ozone column loss is only slightly affected. The O2 and O3 photolysis rate perturbation by sulfate aerosols is shown to be rather sensitive to solar zenith angle. However, since JO2 (which predominantly determines ozone production at the equator) varies several orders of magnitude during the course of the diurnal cycle, using a diurnally averaged solar zenith angle simulates fairly well the volcanic aerosol effect on ozone through photodissociation.¿ 1997 American Geophysical Union