We present a formalism for optical pulse propagation in nonlinear photonic
crystals of arbitrary dimensionality. Using a multiple-scale analysis, we d
erive the dynamical nonlinear Schrodinger equation obeyed by the envelope f
unction modulating an underlying Bloch function. Effective coefficients app
ear in that equation characterizing the effects of Kerr nonlinearity, linea
r gain or loss, and material dispersion. They depend on how the underlying
Bloch function "samples" these effects in the photonic crystal, and require
for their calculation a specification of these effects throughout the phot
onic crystal, and the calculated bandstructure of the photonic crystals in
the linear, nondispersive limit. We show that wave packets from different b
ands can experience significantly modified effective material properties.