  A comparison of AGN detected at gamma ray energies by EGRET with
flat-spectrum radio sources observed in surveys for intraday variability
reveals that a remarkably high fraction of EGRET blazars show significant
interstellar scintillation at centimetre wavelengths. Scintillating AGN will
therefore be targets of interest for GLAST, scheduled for launch in early 2008.
We suggest that the variable, scintillating flat-spectrum radio source PMN
J1326-5256 is associated with the unidentified EGRET source 3EG J1316-5244. We
describe the properties of PMN J1326-5256 and present recent results of
monitoring with the ATCA and Ceduna radio telescopes.
