Situations have important implications for behavior. Recognition of this obvious fact, coupled with the Person-Situation Debate, led to a surge of research on situations during the 1970s, but this research did not yield a useful technique for assessing or comparing the psychological properties of situations. After a hiatus in the 1980s and 1990s, research on situations has been recently reinvigorated (Reis, 2008; Wagerman & Funder, 2009), including the development of the Riverside Situational Q-Sort (RSQ: Wagerman & Funder, 2009). This dissertation puts the RSQ to the test in three different studies. In Study 1 the RSQ is used to assess psychological properties of situations participants experienced in their daily lives and to compute the degree to which those situations are similar to one another. The results indicate that participants behaved more consistently across those situations to the degree to which their situations were more similar. In Study 2 the RSQ is used to assess the properties of situations that promote congruence between one's personality and one's behavior. The results indicate that when a person is in psychological "weak" situations (Mischel, 1977; Snyder & Ickes, 1985) or in situations that promote autonomy, competence, and relatedness to others (Deci & Ryan, 1987), one is more likely to behave in accordance with his or her personality. In Study 3 the RSQ is used to investigate the relationship between personality and unique perceptions of psychological properties of situations. The results indicate that people who are high in well-being tend to view situations they encounter in their daily lives as more positive than people who are low on well-being, or high in negative trait affectivity. Extraverts tend to believe that they are center of attention more so than introverts do. Open people tend to see aesthetic beauty, intellectual stimuli, and lifestyle and political concerns where less open people may not. And narcissists tend to see their situations as opportunities to show off and control others more often than less narcissistic persons do. Taken together, these studies demonstrate the usefulness of the RSQ for assessing psychologically meaningful properties of situations and for testing psychological theory.