ABSTRACT A taxonomy of personality-relevant situations will provide a valuable complement to the taxonomy of personality attributes. To identify some of the most important modifying factors, we asked laypersons what modifies expression of their own traits. Spontaneously generated situation descriptors were elicited from 77 university students, leading to over 7,000 reports of situations. We determined the most frequently occurring words and phrases, and developed initial classification categories. Next, we tested the reliability of the categories, and made refinements to focus on those that proved most reliable. Based on results, we propose that situation descriptions involve at least four separable broad domains of variables—locations, associations, activities, and passively experienced processes—each of which appears to have distinct linguistic markers.