Study: To compare care seeking and non-care seeking couples with infertility in order to describe potential differences which may have consequences for health care planning and research. Design: multicentre surveys of randomly selected women of child-bearing age. Setting: seven centres in five countries: Denmark, Germany (two centres), Italy (two centres), Poland and Spain. Data were collected from 1991 to 1993 as part of a European concerted action. Participants: population-based samples of women between 25 and 44 years. The samples ranged from 442 women in Poland to 2, 729 women in Italy. The participation rates ranged from 54% in Germany to 88% in Poland. Data: data were collected during face to face interviews by means of highly structured questionnaires. Questions were asked about life style factors, work exposures, pregnancy history, fecundity and care seeking behaviour. Main outcome measures: seeking medical advice and help for infertility among couples who had tried to become pregnant for more than 12 months. Main results: nulliparity was the strongest predictor for seeking help in all the European centres and more than 50% of the nulliparous women sought help in all the centres. The frequency of care seeking among couples with secondary infertility varied to a large extent between the different centres. Women with a paid job and smokers were less likely to seek help in most centres (except in Spain and Italy). Conclusion: far from all those with an infertility problem seek medical advice and help, and the correlates of care seeking differ to a large extent between different cultural and health care settings. Research based upon clinical samples could easily be biased if the topic of research correlates with care seeking behaviour.