  We analyze the critical properties of the three-dimensional Ising model with
linear parallel extended defects. Such a form of disorder produces two distinct
correlation lengths, a parallel correlation length $\xi_\parallel$ in the
direction along defects, and a perpendicular correlation length $\xi_\perp$ in
the direction perpendicular to the lines. Both $\xi_\parallel$ and $\xi_\perp$
diverge algebraically in the vicinity of the critical point, but the
corresponding critical exponents $\nu_\parallel$ and $\nu_\perp$ take different
values. This property is specific for anisotropic scaling and the ratio
$\nu_\parallel/\nu_\perp$ defines the anisotropy exponent $\theta$. Estimates
of quantitative characteristics of the critical behaviour for such systems were
only obtained up to now within the renormalization group approach. We report a
study of the anisotropic scaling in this system via Monte Carlo simulation of
the three-dimensional system with Ising spins and non-magnetic impurities
arranged into randomly distributed parallel lines. Several independent
estimates for the anisotropy exponent $\theta$ of the system are obtained, as
well as an estimate of the susceptibility exponent $\gamma$. Our results
corroborate the renormalization group predictions obtained earlier.
