  The recent high precision SMC data on polarized $\mu p$ scatterings have
again confirmed that very little of the proton spin is carried by quarks. To
unravel the mystery of the proton spin structure, it is quite important to know
the behavior of the polarized gluon distribution. By using the positivity
condition of distribution functions together with the unpolarized and polarized
experimental data, we restrict the $x$ dependence of the polarized gluon
distribution.
