Ozone, chlorine monoxide, methane, and submicron particulate concentrations were measured in the stratospheric plume wake of a Delta II rocket powered by a combination of solid (NH4ClO4/Al) and liquid (LOX/kerosene) propulsion systems. We apply a simple kinetics model describing the main features of gas-phase chlorine reactions in solid propellant exhaust plumes to derive the abundance of total reactive chlorine in the plume and estimate the associated cumulative ozone loss. Measured ozone loss during two plume encounters (12 and 39 minutes after launch) exceeded the estimate by about a factor of about two. Insofar as only the most significant gas-phase chlorine reactions are included in the calculation, these results suggest that additional plume wake chemical processes or emissions other than reactive chlorine from the Delta II propulsion system affect ozone levels in the plume. ¿ 2000 American Geophysical Union