We have grown epitaxial (0001)-oriented films of the ferromagnetic intermetallic compound MnSb on GaAs(111) substrates. The ex situ grown samples can be reprepared in such a way that clean, ordered, and magnetically saturated surfaces are obtained. Using spin-resolved photoemission, Sb5p- and Mn3d-derived spectral features are identified, and large exchange splittings (1.4 and 1.7 eV for Mn-Sb bonding states and about 3.0 eV for Mn nonbonding states) are measured. Our ab initio band-structure calculation agrees rather well with the experiment, reproducing the exchange splittings of Mn-Sb states but slightly underestimating that of Mn states.