  The longitudinal interlayer magnetoresistance $R_{zz}(B_{z})$ is calculated
in strongly anisotropic layered metals, when the interlayer band width $4t_{z}$
is less than the Landau level separation $\hbar \omega_{c}$. The impurity
scattering has much stronger effect in this regime than in 3D metals and leads
to a linear longitudinal interlayer magnetoresistance $R_{zz}\propto B_{z}$ in
the interval $\hbar \omega_{c}>4t_{z}>>\sqrt{\Gamma_{0}\hbar \omega_{c}}$
changing to a square-root dependence $R_{zz}\propto B_{z}^{1/2}$ at higher
field or smaller $t_{z}$. The crossover field allows to estimate the interlayer
transfer integral as $t_{z}\sim \sqrt{\Gamma_{0}\hbar \omega_{c}}$.
Longitudinal interlayer magnetoresistance, being robust to the increase of
temperature or long-range disorder, is easy for measurements and provides a
useful tool to investigate the electronic structure of quasi-two-dimensional
compounds.
