The aim of the study was to examine the prevalence and self-reported causes of loneliness among Finnish older population. The data were collected with a postal questionnaire from a random sample of 6,786 elderly people (>or=75 years of age). The response rate was 71.8% from community-dwelling sample. Of the respondents, 39% suffered from loneliness, 5% often or always. Loneliness was more common among rural elderly people than those living in cities. It was associated with advancing age, living alone or in a residential home, widowhood, low level of education and poor income. In addition, poor health status, poor functional status, poor vision and loss of hearing increased the prevalence of loneliness. The most common subjective causes for loneliness were illnesses, death of a spouse and lack of friends. Loneliness seems to derive from societal life changes as well as from natural life events and hardships originating from aging.