Right-to-carry (RTC) laws mandate that concealed weapon permits be granted to qualified applicants. Such laws could reduce the number of mass public shootings as prospective shooters consider the possibility of encountering armed civilians. However, these laws might increase the number of shootings by making it easier for prospective shooters to acquire guns. We evaluate 25 RTC laws using state panel data for 1977 through 1999. We estimate numerous Poisson and negative binomial models and find virtually no support for the hypothesis that the laws increase or reduce the number of mass public shootings.