  In this thesis, we have investigated the higher twist structure functions in
the recently developed method based on light-front Hamiltonian QCD. Because of
various special properties of light-front QCD, this is a more intuitive
approach towards deep inelastic scattering but has a well defined field
theoretic calculational procedure. Because our method is different from the
conventional one, we have obtained various new results. Also, it is easier to
explore many aspects which are difficult to understand in the conventional way.
The structure functions, twist four $F_L$ and $g_T$ contain non-trivial
interaction dependence in the operator structure and therefore involve
quark-gluon dynamics. We have shown that the intergrals of these are directly
related to the light-front Hamiltonian density and transverse spin operator
respectively. These are non-perturbative relations. We have also renormalized
the twist four longitudinal structure function and the full transverse spin
operator respectively upto one loop in light-front Hamiltonian perturbation
theory. We have investigated twist four $F_L$ for bound states like a meson in
1+1 dimensional QCD and for a positronium in 3+1 dimensional QED.
