Awareness of risk factors for loneliness is a prerequisite for preventive action. Many risk factors for loneliness have been identified. This paper focuses on two: poor health and widowhood. Preventive action by developing a satisfying social network requires time and effort and thus seems appropriate for people unexposed to risk factors, i.e. third agers and non-lonely persons. The third age is the period in old age after retirement, before people's social relationships deteriorate. This paper addresses three questions: Are older adults aware of poor health and widowhood as risk factors for loneliness? Are there differences in awareness between third and fourth agers? Are there differences in awareness between lonely and non-lonely older adults? After being introduced to four vignette persons, 920 respondents from the Longitudinal Aging Study Amsterdam were asked whether they expected these persons to be lonely. Older adults, especially third agers, expected peers exposed to the risk factors to be lonely more often than peers who were unexposed. The results indicate that awareness of loneliness-provoking factors is high among third agers, which is a first step towards taking actions to avoid loneliness. Compared to lonely older adults, non-lonely ones expected peers to be lonely less often, suggesting the latter's lower awareness of the risk factors. The results provide evidence for policy makers and practitioners that combating loneliness might require early action. Copyright © Cambridge University Press 2013.