Surprisingly, until now there has never been an empirical study of "creepiness." An international sample of 1341 individuals responded to an online survey. Males were perceived as being more likely to be creepy than females, and females were more likely to associate sexual threat with creepiness. Unusual nonverbal behavior and characteristics associated with unpredictability were also predictors of creepiness, as were some occupations and hobbies. The results are consistent with the hypothesis that being "creeped out" is an evolved adaptive emotional response to ambiguity about the presence of threat that enables us to maintain vigilance during times of uncertainty. (C) 2016 Elsevier Ltd. All rights reserved.