Since November 1993 the Blackbeard instrument aboard the ALEXIS satellite has detected pairs of pulses in the VHF band, known as Trans-Ionospheric Pulse Pairs (TIPPs). These pulses exhibit dispersion consistent with a source of sub-ionospheric origin. As of January 1997 over 850 TIPPs have been detected. The source of these emissions still remains a mystery, although it is believed that TIPPs are in some way related to thunderstorms as such storms provide a strong sub-ionospheric source and produce radiation in the same frequencies observed by Blackbeard. In an attempt to establish this connection we compare the geographic occurrence of TIPPs to that of lightning flashes observed from space by the Optical Transient Detector (OTD) on the Microlab-1 spacecraft. TIPP data run from 2 November 1993 to 19 November 1996. OTD data run from 1 May 1995 to 30 November 1996. The geographical occurrence of TIPPs and that of lightning flashes is strongly correlated. TIPPs occur less frequently during the winter months and their region of production moves southward in the North American sector similar in behavior to lightning activity. ¿ 1997 American Geophysical Union