DESPITE many experimental and theoretical studies, a widely accepted explanation of ball lightning has yet to be found. It is possible, however, that ball lightning is created by the interaction of different types of energy in the atmosphere1. Indeed, the production of a fireball by an electric discharge in an atmosphere containing dilute fuel gases such as propane has been reported2. We have also managed to produce several types of fireball by setting off electric discharges in an atmosphere containing aerosol with varying concentrations of ethane and/or methane3. Here we report the production of plasma fireballs in a natural atmosphere by microwave interference. The fireballs exhibited certain properties that match eyewitness observations of ball lightning, such as motion against the wind and the ability to pass through a wall intact.