Much information is available about physical and functional health among very old adults, but little knowledge exists about the mental health and mental health changes in very late life. This study reports findings concerning positive and negative affect changes among centenarians. Nineteen centenarians from a Midwestern state participated in four assessments over a 6-month period. Positive and negative affect, as well as physical activity, financial resources, mental status, and health were assessed at baseline and during four consecutive time points. Mean individual growth curves suggested mean decreases in positive affect, but no changes were observed in negative affect. Physical activity, financial resources, and self-rated health were associated with growth-curve changes in affect. Centenarians with fewer resources were more likely to show decreases in positive affect. Surprisingly, physical activity and health were associated with increases in negative affect over time. The results suggest that continued activity, high levels of financial resources, and self-rated health are important components in affective states among very old adults. (Contains 3 tables and 2 figures.)