This study examined the development of implicit epistemologies of Finnish adults during the last ten years. It was hypothesized that specific adult experiences are stimulating for development. Moreover, a person's exploratory orientation was hypothesized to be related to development. Kitchener and King's model and method of Reflective Judgment provided tools to study adolescents' and adults' epistemologies and their possible development. Participants (N = 59) were given initial (1986–1988) and follow-up (1993–1994) Reflective Judgment interviews. The age range was from 24–50 years in the follow-up groups. The Reflective Judgment mean stage scores clearly increased during the two study periods (M1 = 4.64,M2 = 5.10; F(1, 58) = 32.82, p = .000). Education, in particular education beyond a person's primary profession/occupation, was a strong predictor of development. Also, encountering diversity and exploratory orientation were related to development, but their connections were more complicated. No gender differences were found. The results support the idea that positive changes in thinking and reasoning take place during adulthood.