This paper describes the realization of the baseline survey of the study ‘PinK - Paare in Kinderwunschbehandlung’ (couples undergoing fertility treatment). The study aims at a broader and better understanding of the situation of couples with an unfulfilled desire to have a child and of pathways leading couples to the fertility clinic. The approach of the study is interdisciplinary. It is designed as a prospective cohort study in a clinical setting. The study population consists of couples with an unfulfilled desire to have a child who presented themselves in a fertility clinic in the German state of Rhineland-Palatinate (RP) or in the capital city of the state of Hesse between July 2012 and May 2013. Self-administered questionnaires were used to gather information from patients at fertility clinics. These were handed out to the patients by the staff at the fertility clinics. Questionnaires returned by the end of July 2013 were included in the data set. The final sample consists of 323 female and 242 male respondents. In 234 couples, both partners participated. The overall response rate is 31%, with considerable variation across the clinics - reasons for and consequences of this are discussed. The final sample is described in terms of the distribution of core socio-demographic variables.