Background. The desire to care for people, a family history of professional health care work, and security in career choice are documented reasons for entering nursing. Reasons for leaving include workload, unsafe work environments and harassment. The relationship between these factors and the time nurses spend in the profession has not been explored. Aim. This paper reports a study with people who have left nursing, to investigate why they became a nurse, how long they stayed in nursing, and their reasons for leaving. Method. A questionnaire was mailed to Registered Nurses currently working outside nursing, seeking respondents' reasons for entering and leaving nursing, and perceptions of the skills gained from nursing and the ease of adjustment to working in a non-nursing environment. Data analysis included descriptive statistics, exploratory and confirmatory factor analysis, correlational analysis and linear and multiple regression analysis. Results. A model incorporating the factors 'altruistic reasons', 'default choice' and 'stepping stone' explained 36Ʋ% of the variance in reasons for becoming a nurse. A model incorporating the factors 'legal and employer', 'external values and beliefs about nursing', 'professional practice', 'work life/home life' and 'contract requirements' explained 55ƴ% of the variance in reasons for leaving nursing. Forty-eight per cent of the variance in tenure in nursing practice was explained through personal characteristics of nurses (36%), reasons for becoming a nurse (7%) and reasons for leaving (6%). Conclusion. The reasons why nurses entered or left the profession were varied and complex. While personal characteristics accounted for a large component of tenure in nursing, those managing the nursing workforce should consider professional practice issues and the balance between work life and home life.