First, 9 of the 11 EGRET-identified sources listed by Thompson et
al. [1995], which have been well studied with VLBI, are known or
possible superluminal radio sources [Vermeulen & Cohen 1994; Barthel
et al. 1995; this work]. The mean apparent speed in the VLBI
jets of these 11 EGRET-identified sources is 5.6h 
c with a
standard deviation of 7.3h c.
While there is substantial evidence that some EGRET-identified sources are highly beamed, some others do not appear to be. Some of
the strong EGRET sources, for example 1226+023 (e.g. Unwin et al.
1985) are clearly highly superluminal whereas others such as 1222+216
[Hooimeyer et al. 1992] are perhaps consistent with subluminal speeds.
Second, there are some highly superluminal radio sources that have not been identified
by EGRET, such as 1641+399 [Biretta, Moore & Cohen 1986]. The mean apparent speed for
the core selected quasars and BL Lac objects which are listed by
Vermeulen and Cohen [1994] and have not been identified by EGRET is
3.9h c, with a standard deviation of 3.0h c (based on 24
objects and using the same method as for the EGRET-identified sources).
These data do not allow a firm conclusion to be made regarding possible
differences or similarities in beaming characteristics between the radio sources EGRET has identified and those not identified. The mean values for the apparent VLBI speeds are
easily consistent at the 1 
level, but the standard deviations
on the distributions are large.
For the sake of completeness, an apparent speed of 
(for the EGRET- identified sources) corresponds to a minimum intrinsic speed of 
for the radiating material and a maximum angle to the line of sight of 
for the motion. Likewise for the sources not identified by EGRET 
gives 
and 
. Using these limits in the equation for the Doppler factor gives rough values of 
for the EGRET-identified sources of 4.0, and 1.7 for the radio sources not identified by EGRET.