Oral health has generally improved in Sweden over the past 30 years. Investigations of living conditions have indicated that people with chronic mental health problems requiring psychiatric services diverge from that pattern. Research into oral health-related quality of life in this group might enhance our knowledge of the relationship between oral health, health perceptions, life satisfaction, and oral status, and its impact on quality of life in people with mental health problems. It could contribute to the description and broaden the understanding of the concept quality of life. The overall aims of this thesis were to describe oral health and oral health-related quality of life in persons attending psychiatric outpatient services; and to investigate oral health in relation to its biological aspects and perceived quality of life, including self-related variables and social aspects. Additional aims were to describe how persons with severe mental illness perceive oral health problems and to analyze the support they receive in counteracting dry mouth. The population studied consisted of 113 persons attending outpatient psychiatric services who voluntarily underwent a visual oral examination and a structured interview monitoring different aspects of life. Ten persons took part in a longitudinal investigation of how people with severe mental illness perceive oral health problems and support by means of regular visits aimed to evaluate the increase of such support. The findings showed that people in the total cohort were missing an average of 2.4 teeth. Poor oral hygiene was found in 41% of the group and 44% had objective signs of dry mouth. Seventy percent were assessed to be in need of some kind of dental treatment: 50% were overdue for scaling and polishing, 13% required more extensive dental treatment, and in 7% the need was acute. Routine dental visits were not uncommon: 75% had visited the dentist during the last year. Use of psychopharmceuticals was prevalent: 65% reported taking two or more prescribed 10 drugs. The investigation improved the understanding of psychological aspects associated with oral health among those studied, and showed measurably lower scores on life satisfaction items than is found in the general population. Analyses of the relationships between perceived oral health-related quality of life and biological and psychological factors demonstrated a correlation with numbers of teeth, type of psychiatric diagnosis, and gender. In the study population, number of teeth, life satisfaction, perceived physical health, and gender were found important. In relation to the psychiatric diagnoses, number of teeth was a significant factor in participants diagnosed with mood disorders and within the schizophrenia spectra. In participants diagnosed with anxiety and other psychiatric diagnoses, life satisfaction and reliance on chance were significant. The perception of health explained the variance in males. To females, number of teeth, life satisfaction, dental fear, and reliance on chance were also significant factors. In the study describing experience of oral health and perceived support, the result was illustrated by five categories: feelings and experiences related to poor oral health, experiences of dental care, experience of self-care, strategies for handling poor oral health, and experience of support. Oral health was important to the informants’ ability to relate to their social environment. A compromised dental status caused feelings of shame and stigma. Dental care revealed positive as well as negative experiences associated with the provider’s ability to meet the informant’s special needs. Strategies for dealing with poor oral health were mostly circumventions and were at best given ad-hoc solutions. Receiving support in oral health matters from staff was almost perceived as offensive; oral care reminders were often disregarded in an apparent assertion of the autonomy of informants, even though such behaviour could have negative consequences for their health. In conclusion, the findings showed that dental status, expressed as numbers of missing teeth, was higher for those attending psychiatric outpatient services than in a general population. The need for prophylactic dental treatment was considerable, suggesting that oral health issues need to receive increased attention during the course of psychiatric care in order to treat the whole patient. Experiences of oral health-related quality of life are of importance to the total appreciation of quality of life in an individual. This study might also contribute to the understanding of health problems in an outpatient psychiatric population since the perception of oral health-related quality of life was found to be dependent on the particular psychiatric diagnosis and gender. Questions regarding oral health in people with severe mental illness need to receive increased interest from dental, psychiatric, and social services in order to encourage self-care and enhance the autonomy of individuals.