Spouses of patients experience role strains as a result of informal caregiving, which has been associated with mood in numerous research studies. However, most research is on female caregivers, and little is known about the experience of male spouses, or of the caregiving provided to fibromyalgia patients. The Stress Process Model was used to examine mediators and moderators of the relation between role strain and mood among 135 husbands of women with fibromyalgia. Results indicated that the more activities of daily living and instrumental activities of daily living performed by the husband, the greater the role strain. Role strain was associated with worse mood. A test of the Stress Process Model supported a partial mediation model, where social support and emotion-focused coping partially mediated the relation between role strain and mood. No evidence was found for a moderation model or for problem-focused coping as a mediator. Our research suggests significant impairment and caregiving needs among this patient population, which in turn relates to the mood of the husband who is also an informal caregiver. Our findings also support the Stress Process Model in explaining the complexity of caregiving effects. The results of the study suggest avenues for intervention for individuals strained by their partners' illness.Spouses of chronically ill individuals have poorer mental health than comparison groups and the general population [1,2]. Spouses may be affected because the illness may require informal caregiving, including assistance with activities of daily living (ADLs; such as toileting, dressing), instrumental activities of daily living (IADLs; such as shopping), and taking over responsibilities that the patient can no longer perform (such as cleaning, cooking). These caregiving responsibilities may interfere with spouses' abilities to perform other roles, resulting in role strains.Role strains, experienced daily by most individuals, are defined as the difficulties felt by individuals who have multiple roles with accompanying obligations [3]. For caregivers, the additional responsibility of helping a patient with a health condition may divert much needed resources from the other roles currently fulfilled by the individual, causing role strain. Roles typically examined for strain include work, domestic environment, sexual relations, family relations, and social relations. Of the employed caregiving husbands in a national study of frail elderly, 32% reported working fewer hours, 28% indicated they rearranged their schedule, and 24% took time off without pay because of their wives' illness [4]. In the domestic environment, husbands report an increase in the amount of time spent on household chores as a direct result of their wives' illness or disability [5]. A chronic illness may affect the couple's sexual relations as well. For example, patients with a rheumatic disease listed pain or weakness, fatigue, and lack of interest as the top *Address correspondence to this author at the IUPUI, Department of P...