Trans-Ionospheric Pulse Pairs (TIPPs), as detected by the Blackbeard instrument on board the ALEXIS satellite, correlate with signals that the National Lightning Detection Network (NLDN) classifies as cloud lightning with a positive signal polarity (+IC). Correlation is only found for +IC pulses occurring in the 10 ms interval prior to TIPP occurrence. Apart from this single peak, there is no general change in lightning rates around TIPP time. Correlation between TIPPs and +IC strokes is statistically significant with 99.94% confidence. The amplitudes of +IC pulses that are associated with TIPPs are indistinguishable from the amplitudes of pulses that are not. The rise time of +IC pulses correlating with TIPPs, however, does appear to be longer than the noncorrelating +IC pulses, the median value being about 3 times greater than all other +IC pulses. By assuming TIPPs to be generated close to the detecting ground station, we can use the pulse separation time to calculate the source heights for the ground reflection model. The calculated height of TIPPs is consistent with a cloud source. ¿ 1998 American Geophysical Union