The hadronic background, so-called minijets, has been estimated for the proposed linear
colliders at recent workshops. [16, 10, 4, 5]
Since the calculations depend on the poorly known gluon content of a photon at a small
Feynman x value of less than 0.1, they have a large ambiguity, for instance more than
100%.
For a comparison between various linear colliders, the method of P.Chen
et.al. [17] has been employed as the standard calculation in the TRC
report.
According to the report, the number of minijets are 0.0052 and 0.0032 per a bunch
crossing for JLC-I(c) and TESLA, respectively, with 
GeV and 
5GeV, while the 5GeV hadronic events are 3- and 5-times
more than the minijets.
Since the rates are still low, and, also, the events are boosted in the very forward
angular region, no serious problem is expected at least at 
500GeV.