We have carried out STM and height-barrier imaging on the Cs-absorbed Si(III) 7x7 surface. At small coverages, Cs atoms adsorbed on Si(III) at room temperature tend to form clusters, as previously observed by Hashizume et al. [J. Vac. Sci. Technol. B 9 (1991) 745]. Although they report empty-state images shouting anomalous contrast, no such images are observed in our experiment. The measured barrier height decreases locally above Ca sites and exhibits no long-range Variation around each adsorption site. The average reduction in the barrier height at Cs sites is found to be Delta phi = 0.87 eV.