Sudden and transient decreases of ozone column values were detected over the midlatitudes of South America during the springs of 1996 and 1997 by a network of ground instruments. These low-ozone events were accompanied by air temperature decreases in the lower stratosphere. The analysis of the events suggests a connection with the springtime Antarctic ozone hole. Three-dimensional isentropic back trajectories showed that vertical motion also contributed to the decreases of total ozone observed at the midlatitudes of South America. ¿ 2000 American Geophysical Union