There is an intuitive distinction between knowing someone in a detached manner- impersonally- and knowing someone in a more intimate fashion- personally. The latter seems to involve the specially active participation of the person known in a way that the former does not. In this paper I present a novel, communication account of knowing someone personally that successfully explains this participation. The account also illuminates the propositional and testimonial character of the personal knowledge of persons, the conditions of limited transferability to which such knowledge is subject, and its distinctly meaningful role in everyday life. I conclude by considering a worry about self-knowledge that arises on the communication account.