Acne is a common disease that in cases of extreme disfiguration can have severe consequences for the personality development of young people and is associated with a relatively high prevalence of depression and suicide. Spontaneous regression is common, but acne can extend into the fourth and fifth decades of life. The pathogenesis is still not fully understood. Factors promoting the development of acne are: increased sebum production, ductal cornification, bacterial colonization of the pilosebaceus ducts and inflammation. However, there is evidence that inflammation is not a factor but rather a consequence of the interaction of the other three factors. Propionibacterium acnes releases pro-inflammatory cytokines as well as antigens and mitogen(s), with cellular and non-cellular responses to these products triggering inflammation. Treatment is often frustran. Therapeutical strategies are needed based on new understandings of the pathomechanisms involved in acne. The aim of this review is to summarize the data on aetiopathological factors in acne and their contribution to acne pathology and therapy.