Aim of the study was to explore five- to six-year-old children's understanding and processing of the number zero. To this end we evaluated the acquisition and manipulation of zero as a digit and as a verbal numeral within different contexts, and its understanding as a quantity and as a numerical concept. Results show that the symbolic knowledge of zero is not delayed compared to other small numbers. However, some difficulties emerge in the processing of zero as a number among other numbers as well as in the understanding of its cardinal meaning. This delay can receive different interpretations (e.g., rather abstract processes are required to represent "zero"). Moreover, "zero" shows a numerical special status as syntactic marker in decades as well.