  The two-proton correlation function at midrapidity from Pb+Pb central
collisions at 158 AGeV has been measured by the NA49 experiment. The
preliminary results are compared to model predictions from proton source
distributions of static thermal Gaussian sources and the transport models of
RQMD and VENUS. We obtain an effective proton source size 4.0 +-0.15(stat.)
+0.06-0.18(syst.) fm. The RQMD model underpredicts the correlation function
(source size 4.41 fm), while the VENUS model overpredicts the correlation
function (source size 3.55 fm).
