OBJECTIVE To assess whether the way in which women experience the onset of their labour influences the duration of their labour. METHODS Longitudinal study on a convenient sample of women in spontaneous labour with a singleton pregnancy in cephalic presentation at term. METHODS University hospital in Germany. METHODS Six hundred and fifty-one women (347 primiparae and 304 parae). METHODS Women recorded how and when labour had started. Responses were subjected to structured content analysis. Two investigators independently subdivided women's reported signs and symptoms into eight predefined categories. These data were related to maternal characteristics and to the course and outcome of labour as documented in the perinatal record. METHODS Women's perception of how labour had started, interval between onset of labour and rupture of the membranes and duration of first stage labour and overall duration of labour. RESULTS Only 60% of women reported contractions as a sign of the onset of their labour. These women had a longer interval between the onset of labour and rupture of the membranes but a similar duration of labour when compared with women who did not report contractions as a sign of the onset of labour. Self-reported loss of amniotic fluid was the only sign that showed a consistent relationship with the duration of labour. Other patterns of labour onset had no effect on the duration of labour. CONCLUSIONS Irrespective of whether they have given birth before, women experience their onset of labour in a variety of ways. A large proportion of these experiences bear no resemblance to the classical diagnosis of labour and most are unrelated to the duration of labour.