SUSANNE OLSEN ROPER Brigham Young University JEREMY B. YORGASON Brigham Young University* Older Adults With Diabetes and Osteoarthritis and Their Spouses: Effects of Activity Limitations, Marital Happiness, and Social Contacts on Partners’ Daily Mood Using daily diary data from 28 later life couples where one spouse had diabetes and osteoarthritis, we examined crossover effects of target spouses’ daily activity limitations and their partners’ daily mood. On days when target spouses’ daily activity limitations were higher than average, partners’ positive mood decreased and negative mood increased; when target wives’ limitations were higher than average, husbands’ positive mood was higher. Marital happiness and frequency of telephone conversations of target spouses buffered some relations. Results advance our understanding of daily health processes within later life marriages by identifying crossover effects of activity limitations of an ill spouse with the mood of their partner and underscore the role School of Family Life, 2089 Joseph F. Smith Building, Brigham Young University, Provo, UT 84602 (susanne_olsen_roper@byu.edu). ∗ School of Family Life, 2079 Joseph F. Smith Building, Brigham Young University, Provo, UT 84602. Both authors contributed equally to this research. Key Words: caregiving of the elderly, marital quality, mood, multiple chronic illnesses, social support networks. of marital happiness and social contacts in buffering these associations. A growing literature has examined specific diseases and their effects on married individuals and their spouses (Berg & Upchurch, 2007). Little research, however, has investigated the marital experiences of individuals living with multiple chronic illnesses. This oversight is costly, given that over half of adults aged 65 and older report having at least two chronic illnesses (Hoffman, Rice, & Sung, 1996), and that average life expectancy continues to rise (Yang, 2007), increasing the likelihood of contracting age- related chronic conditions. Most studies of health and marriage examine health events across several months and years. Although major health events, such as hospital visits or surgery, can be influential, daily health events such as illness symptoms, pain, mobil- ity limitations, and medicinal side effects are often overlooked. After diagnosis, the hospital stay, or surgery come the daily, microhealth pro- cesses that accompany management of chronic health conditions and shape individual and part- ner well-being. ‘‘Daily event methodologies’’ have been suggested as an appropriate approach 460 Family Relations 58 (October 2009): 460 – 474