With the increasing popularity of Facebook among adult users and the diverse social networks, especially based on age, that adults form on Facebook, it is important to examine what adult Facebook users have seen on Facebook and deem inappropriate. Previous studies only address college students and most of them involve hypothetical post-scenarios. This study addresses these gaps by examining 190 adult Facebook users from a northeastern Pennsylvania university and asking them to identify the top three types of posts they have (...) seen on Facebook and considered to be inappropriate. Findings suggest that these adults consider sex/nudity, foul language and politics to be inappropriate for Facebook. These mirror values of face-to-face interaction, but are not mentioned in research of online inappropriate behaviour. When more specific themes are combined for group comparisons, two additional themes, social issues and aggression which are also generally unexplored in the research, emerge as inappropriate as well. However, with the exception of gender and educational differences in the perceptions of sex/nudity, there are few group differences in the observed Facebook posts that these adults find to be inappropriate. Implications for online interaction and future research are discussed. (shrink)