SERENDIP IV is the latest phase of Berkeley's SERENDIP endeavor which was installed at the Arecibo radio telescope in June 1997. It is 40 times more sensitive than its predecessor, SERENDIP III, and examines 168 million frequency channels every 1.7 seconds in a 100 MHz band centered at 1.42 GHz. Signals that peak significantly above the background noise are stored and the data transferred across the Internet to the SERENDIP laboratory at Berkeley. There the data are passed through a series of algorithms designed to reject radio frequency interference and sift out signals that have some possibility of being both artificial and extraterrestrial. SERENDIP IV instrumentation is also being used by the Australian SETI group at the Parkes Telescope and by the Italian SETI group at Medicina. A 4-million-channel version of SERENDIP IV is in operation at the Ohio State University Radio Observatory.