A passive sporadic E detection technique based on a Global Positioning System (GPS) receiving system has been developed and tested in a midlatitude environment. This system detects the small-scale total electron content, TEC, variations believed to be produced by electron density structures associated with sporadic E. The current GPS detection technique was able to detect ionosonde-detected sporadic E conditions for 73% of the cases at high-elevation look angles in a set of midlatitude summer observations. Several approaches have been identified that may significantly improve this detection ratio. These approaches include reducing GPS phase multipath, implementing time and space averaging, and investigating the use of high-speed GPS TEC measurements. This technique provides a basic sporadic E detection functionality for applications where an ionosonde is not available. It also provides complementary ionospheric information in regions outside the ionosonde viewing area for applications where an ionosonde is available. ¿ American Geophysical Union 1995