Pupillometry monitoring under general anesthesia is based on the assumption that pupillary diameter variations reflect the adequacy of the provided analgesia to the intensity of the nociceptive surgical stimulus. The accurate interpretation of pupillometric data requires establishing clearly what the expected baseline unstimulated pupillary diameter at each specific level of hypnosis is. Opioids decrease pupillary diameter in a dose-dependent fashion. In contrast, the effects of hypnotic drugs on pupillary diameter are not well known. Our aim was to describe the potential relationship between propofol predicted effect-site concentrations (Cets) ranging from 1 to 3 µg/mL and pupillary diameter.