Background: dsd-LIFE is a comprehensive cross-sectional clinical outcome study of individuals with disorders/differences of sex development (DSD). This study focuses on various rare genetic conditions characterized by impaired gonadal or adrenal functionality. Methods/Design: The study aims to assess quality of life (QoL) as a measure of psychosocial adaptation, psychosexual and mental health aspects as major outcomes. Health status and functioning, medical and surgical therapies, participants' views on health care, psychological and social support, sociodemographic factors and their interrelations will be investigated as factors associated with the outcomes. In addition, ethical considerations in the field of DSD are addressed and previous experiences with health care were gathered. One thousand and forty participants with different DSD conditions were recruited by 14 study centres in 6 European countries (France, Germany, the Netherlands, Poland, Sweden and the United Kingdom) from February 2014 until September 2015. The conditions included were: Turner syndrome (n=301); 45,X0/46,XY conditions (n=45); Klinefelter syndrome (n=218); 47,XYY (n=1); 46,XY gonadal dysgenesis/ovotestes (n=63); complete androgen insensitivity (CAIS) (n=71); partial androgen insensitivity (PAIS) (n=35) and androgen synthesis disorders (n=20); severe hypospadias (n=25); other or non-classified 46,XY DSD (n=8); 46,XX congenital adrenal hyperplasia (CAH) (n=226); 46,XX gonadal dysgenesis/ovotestis (n=21); and 46,XX in males (n=6). For an add-on study, 121 46,XY male-assigned individuals with CAH due to 21-hydroxylase deficiency were recruited. Mean age of participants' was 32.4 (+/-13.6years). Discussion: Participation was high in conditions not commonly described as DSD, such as Turner and Klinefelter syndromes or CAH. Recruitment of individuals with XY DSD conditions proved to be more difficult. The data collection of PROs resulted in high data quality. Within medical and physical examination data, more missings and/or inaccurate data were found than expected. The European dsd-LIFE study recruited and evaluated the largest cross-sectional sample of individuals with different conditions classified under the term DSD. The data from this large sample will provide a sufficient basis for evidence-based recommendations for improvement of clinical care of individuals affected by a DSD condition. Trial registration: German Clinical Trials Register DRKS00006072.