Based on long-term series of photoelectric observations of the UX Ori stars BF Ori, RR Tau, and CO Ori, we obtained evidence for the cyclicity of their photometric activity on a time scale from several years to ten years or more. Since the photometric variability of this type of star is attributable to variable circumstellar extinction and is determined by the instantaneous dust column density, the presence of activity cycles points to the existence in circumstellar dust disks of large-scale nonuniformities in the dust distribution which periodically appear on the line of sight. The components of a binary (or multiple) system or protoplanets can be the source of such nonuniformities.