Bursts of proton (0.6<Ep<3.4 MeV) were observed sunward of Jupiter's bow shock out to 200 Rj radial distance by the University of Iowa detector G on Pioneer 11. These observations supplement earlier reports by the University of Chicago and Goddard Space Flight Center groups and strengthen their suggestion of Jovian origin by virtue of our findings that the protons exhibit a very anisotropic, field-aligned pitch angle distribution directed away from the planet and that the bursts are not associated with interplanetary disturbances. Power spectra of the proton counting rates show no significant power at Jupiter's rotational period.