  Non-leading contribution to the pion electromagnetic form factor which comes
from the pion twist-3 wave function is analyzed in the modified hard scattering
approach (MHSA) proposed by Li and Sterman. This contribution is enhanced
significantly due to bound state effect (the twist-3 wave function is
independent of the fractional momentum carried by the parton and has a large
factor $\sim m_\pi^2/m_0$ with $m_\pi$ being the pion meson mass and $m_0$
being the mean u- and d-quark masses). Consequently, although it is suppressed
by the factor $1/Q^2$, the twist-3 contribution is comparable with and even
larger than the leading twist (twist-2) contribution at intermediate energy
region of $Q^2$ being $2 \sim 40 {GeV}^2$.
