  We have tested the theoretical values of critical exponents, predicted for
the three--dimensional Heisenberg model, based on the published Monte Carlo
(MC) simulation data for the susceptibility. Two different sets of the critical
exponents have been considered - one provided by the usual (perturbative)
renormalization group (RG) theory, and another predicted by grouping of Feynman
diagrams in phi^4 model (our theory). The test consists of two steps. First we
determine the critical coupling by fitting the MC data to the theoretical
expression, including both confluent and analytical corrections to scaling, the
values of critical exponents being taken from theory. Then we use the obtained
value of critical coupling to test the agreement between theory and MC data at
criticality. As a result, we have found that predictions of our theory
(gamma=19/14, eta=1/10, omega=3/5) are consistent, whereas those of the
perturbative RG theory (gamma=1.3895, eta=0.0355, omega=0.782) are inconsistent
with the MC data. The seemable agreement between the RG prediction for eta and
MC results at criticality, reported in literature, appears due to slightly
overestimated value of the critical coupling. Estimation of critical exponents
of 3D Ising model from complex zeroth of the partition function is discussed. A
refined analysis yields the best estimate 1/nu=1.518. We conclude that the
recent MC data can be completely explained within our theory (providing
1/nu=1.5 and omega=0.5) rather than within the conventional RG theory.
