The hydrolysis of BrONO2 on sulphate aerosols has been included in a 2-D model calculation of ozone changes over the period 1980--1995. Inclusion of this reaction has only a marginal impact on the calculated ozone trends between 1980 and 1990. The effect of the reaction on an atmosphere which has been heavily perturbed by sulphate aerosols for the period June 1991--1995 has been examined by using the idealized WMO 1995 scenario. The results show that the addition of this reaction has a major impact on the calculated transient ozone loss under enhanced aerosol conditions and approximately doubles the calculated ozone loss between 60¿S and 60¿N in 1992 (when maximum loss of ozone occurs). In contrast to the effects of the hydrolysis of N2O5, the effects of the hydrolysis of BrONO2 are most marked at high latitudes in summer. ¿ American Geophysical Union 1996