(100) and (110) single crystals of silver were cleaned by electron and argon‐ion bombardment in ultra‐high vacuum. The work functions of the bulk crystals, and of silver films formed upon them by autoepitaxy, were determined photoelectrically. The bulk crystals had work functions of (4.64 ± 0.02) eV and (4.52 ± 0.02) eV respectively. The effect of the deposition of silver films was to reduce the work function, but continued cycles of deposition and annealing at 500 to 600 K caused the work function to return to a value very close to that of the bulk crystal. An annealed film of silver deposited in stages on a mica substrate at 425 K had a work function of (4.72 ± 0.02) eV, corresponding to that of the (111) silver surface. If the mica remained at room temperature during deposition, the work function was about 4.5 eV. The work function of a thick polycrystalline film of silver on quartz was (4.26 ± 0.02) eV. The results support the Smoluchowski correlation of work function with surface atom density.