The communication of risk is a central activity in clinical genetics, with genetic health professionals encouraging the dissemination of relevant information by individuals to their at-risk family members. To understand the process by which communication occurs as well as its outcomes, a systematic review of actual communication in families about genetic risk was conducted. Findings from 29 papers meeting the inclusion criteria were summarised and are presented narratively. Family communication about genetic risk is described as a deliberative process, in which: sense is made of personal risk; the vulnerability and receptivity of the family member is assessed; decisions are made about what will be conveyed; and the right time to disclose is selected. The communication strategy adopted will depend on these factors and varies within families as well as between families. Inherent in these processes are conflicting senses of responsibility: to provide potentially valuable information and to prevent harm that may arise from this knowledge. However, the research 'outcomes' of communication have been professionally determined (number of relatives reported as informed, uptake of testing, knowledge of the recipient) and are typically unrelated to the concerns of the family member. The impact of communication on the individual, family members, and family relationships is of concern to the individual conveying the information, but this is largely self-reported. Currently, there is insufficient information to inform the development of theoretically and empirically based practice to foster 'good' communication. The implications for future research are discussed.