One of the most salient topics in tourism studies is the analysis of factors driving tourist expenditure decisions, given their impact on destinations and the consequences for marketing strategies. Tourist expenditure in a given destination is the result of considering both the length of stay and the daily expenditure. The objective of this research is to analyse daily tourist expenditure determinants using a survey of foreign tourists visiting one leading destination in Southern Europe: the Spanish Mediterranean coast. It focuses on two aspects: how the length of stay influences daily expenditure and how the different activities of tourists during their stay affect tourist expenditure. The research employs a dataset of nearly 184,000 observations covering 2004-2009 and includes tourist socio-economic characteristics and elements related to the trip. The results confirm that tourist expenditure is explained by a set of tourist-related social and economic factors and these factors shed light on the consequences of strategies to extend the length of stay of tourists. Finally, the effect on the daily expenditure of tourists' activities helps to determine the complementary supply (health, culture, gastronomy, etc) that must accompany mature sun-and-sand destinations.