In previous research I have theorised that there is a three-step motivational sequence that drives fertility behaviour, beginning with motivational traits, continuing with fertility desires and concluding with fertility intentions. In this article I focus on four properties of fertility desires and intentions, examining some recent research findings that bear on the similarities and differences between these two constructs. The four properties include the degree to which either construct has direct genetic antecedents, the degree to which either construct directly predicts behaviour, what type of dimension is used to measure each construct, and the effects that each construct has on the individual's satisfaction with being pregnant. The findings regarding these four properties suggest that fertility desires are intermediate between two evolutionally distinct motive systems that drive reproductive behaviour. The findings also suggest additional research questions that require further pursuit. Finally, the findings inform certain fertility-related policy issues, in particular the gap between desired or intended fertility and actual fertility. 1 This article is based on an invited presentation at the conference "From intentions to behaviour: reproductive decision-making in a macro-micro perspective" organised by the Vienna Institute of Demography and the international project REPRO and held in Vienna, Austria, on December 2-3, 2010.