Objective: To describe lifetime and 12 month prevalence of common DSM-IV mental disorders, their demographic correlates, and association with service utilisation and disability in Australians aged 65-85 years of age. Methods: The sample included Australian residents aged 65-85 years who participated in the 2007 Australian National Survey of Mental Health and Well-being (n=1905). The prevalence of DSM-IV mental disorders was estimated using the lay-interviewer administered World Mental Health version of the Composite International Diagnostic Interview. Results: Eight percent had experienced an affective disorder, 10% an anxiety disorder, and 12% a substance use disorder at some point in their life. Sex, age, and marital status were significant correlates of any lifetime mental disorder. Approximately, 2%, 4%, and 1% of old age respondents met criteria for mood, anxiety, and substance use disorders in the past 12 months, respectively. The presence of physical disorder, disability, and greater treatment service use were associated with any mental disorder in the past 12 months. Prevalence of lifetime and 12 month disorders by age band revealed a decrease as age increased. Conclusions: A substantial number of community dwelling old age Australians have experienced a mental disorder in their lifetime. Demographic correlates of mental disorder were relatively consistent between lifetime and 12 month prevalence of disorders, although sex made less of an impact and the presence of physical disorders more of an impact in recent disorders. Twelve month prevalence data suggest that a high proportion of old age Australians still experience mental disorders, predominantly anxiety and major depression.