Objective. To describe the effects and side-effects of the continuous use of oral contraceptives. Design. A review of articles concerning oral contraceptives taken continuously or in cycles with hormones taken for more than 21 days per cycle. Methods. We searched publications in PubMed and Embase. Randomized controlled trials were selected if possible, otherwise case–control studies or cohort studies with controls were chosen. A level of evidence as described by the Centre for Evidence Based Medicine (Oxford University, Oxford, UK) was assigned to all selected studies. Main outcome measures. Clinical and paraclinical effects and side-effects of oral contraceptives administered continuously. Results. The studies suggest that the endometrium is inactive during continuous use of oral contraceptives and the risk of endometrial hyperplasia is not increased. Numbers of bleeding days are halved with continuous use; however, spotting and irregular bleeding are more often seen in the beginning of use, decreasing with time. Hemostatic parameters and serum lipid and carbohydrate profiles in continuous and conventional users do not differ. Menstrual cycle-related symptoms are relieved better by continuous treatment. After surgery for endometriosis, the effect of continuously used oral contraceptives on the risk of recurrence of pain has been found to be less than that of gonadotropin-releasing hormone (GnRH) analogues, but better than the rate seen during conventional cyclic use. Conclusion. Oral contraceptives taken continuously or in long cycles seem to offer benefits with regard to menstrual symptoms and the recurrence of symptoms related to endometriosis. Long-term studies, comprising large groups of women, are lacking.