  We investigate the effect of a constant external non-Abelian field on chiral
symmetry breaking in a (2+1)-dimensional Nambu-Jona-Lasinio model and in 3D QCD
by solving the gap equation and the Bethe-Salpeter equation, and also by RG
analysis. In the (2+1)-dimensional NJL model chiral symmetry breaking occurs
for any weak coupling constant but in 3D QCD catalysis of chiral symmetry
breaking does not occur.
