Spain has one of the highest levels of early school leaving and educational failure of the European Union. The purpose of this paper is to analyse the anatomy of early school leaving in Spain and its characteristics. In order to do so, in the first part we discuss the measurement problems related with this concept and the evolution of drop-out rates in Spain. We argue that the published figures of early school leaving slightly underestimate the phenomenon, and discuss the impact of the increase in immigration rates on the level of educational failure and its very unequal distribution in terms of gender. In a second part, using data from the Labour Force Surveys of 2000 and 2007, we explore the factors behind educational failure by means of a logistic regression. The results of this model confirm the explanatory power of social reproduction hypotheses, but also show that there are important aspects of the patterns and recent evolution of early school leaving which cannot be explained by a single theoretical approach. (Contains 2 tables, 3 figures, and 4 notes.)