Abstract: This article discusses the important role that preconceptions play in the process by which students learn to be nurses. The importance of preconceptions emerged from the analysis of data in a grounded theory study that sought to gain a greater understanding of how undergraduate student nurses in New Zealand experienced and responded to differences they perceived between the theory and the practice of nursing. It became clear that the preconceptions each student nurse held about the nature of nurses and nursing care were the standards against which the worth of the formal, practical and personal theories to which students were exposed during their nursing degree was evaluated. It was clear that preconceptions functioned as the mediator between the intentions of nursing education and the learning that eventuated for each student from practicum experiences. The implications for nursing education, for which preconceptions are not generally highly valued as a basis for learning about professional nursing, are that the individual experience and personal characteristics of each student receive significant focus when a nursing programme is planned. This means that the orthodox principles that underpin the design of nursing curricula should be reviewed and an overtly constructivist perspective adopted for nursing education for which the prior experiences of the student are the starting point.