Brown adipose tissue (BAT) is physiologically present and active in adult humans. The stimulation of BAT in man can potentially increase total daily energy expenditure and is seen as a possible target to treat obesity. Altered BAT activity is also related to other diseases and therefore the therapeutic potential of BAT could reach beyond obesity. This is supported by both in vitro and in vivo reports from animal studies, describing the possible role of BAT in both physiology and pathophysiology. In addition, since the discovery of functional BAT several clinically relevant studies have been conducted in adult man. Clinical observations report BAT activity under multiple conditions, suggesting BAT could be important in the onset and/or treatment of diseases related to the metabolic syndrome, thyroid disorders, cancer and immune system dysfunction. This review highlights those diseases or syndromes in which BAT may play a role in relation to prevention, diagnosis or therapy, by translating basic research into clinical relevance.