To prepare the care system for a rising population of older people, it is important to understand what factors predict the use of care. This paper reports a study of transitions in the use of informal and professional care using Andersen-Newman models of the predictive predisposing, enabling and need factors. The study has drawn on Longitudinal Ageing Study Amsterdam (LASA) data on the use of care and the contextual factors. The data were collected at three-yearly intervals from a random, sex- and age-stratified, population-based sample of adults aged 55-85 years. In summary, the findings for those who initially did not receive care were that almost one-third received some kind of care three years later, most of which was provided by informal care-givers. Need factors were important predictors of most transitions in care, and predisposing and enabling factors, such as age, partner status and income, also played a role. On the relationship between informal and professional care, evidence was found for both 'compensatory processes', i.e. informal care substitutes for professional care, and 'bridging processes', i.e. informal care facilitates professional care. In view of the increasing discrepancy between the demand for professional care and its supply, the significant impact of predisposing and enabling factors offers opportunities for intervention. © 2005 Cambridge University Press.