Theorists and researchers have developed abstract divisions in the life span to mark significant stages. To explore the conceptual labels individuals use to make divisions in their life spans, 92 adults, aged 20 to 55 years, marked significant milestones on a lifeline. Participants also completed a demographic questionnaire. Data on the labels used and the frequency of responses were tallied. An analysis of the results showed that subjects did not employ the age periods or conceptual stages derived by researchers but instead used events or milestones that fell into four social categories: school, marriage, children, and career/jobs. Subjects used significantly more milestones from their past than their future. The age of the respondent was not reflected in the number of milestones used but rather in the distribution between past and future. These findings suggest that the subject's perspective may be useful in understanding changes in adulthood. (BL)