  We compute the four loop term of the mass anomalous dimension in the two
dimensional Gross-Neveu model in the MSbar scheme. The absence of
multiplicative renormalizability which results when using dimensional
regularization means that the effect of the evanescent operator, which first
appears at three loops in the 4-point Green's function, has to be properly
treated in the construction of the renormalization group function. We repeat
the calculation of the three loop MSbar beta-function and construct the
beta-function of the evanescent operator coupling which corrects earlier
computations.
