In this paper, I study dynamic common-value contests. Agents arrive over time and expend efforts to compete for prizes that are allocated proportionally according to efforts exerted. This model can be applied to a number of examples, including rent-seeking, lobbying, advertising, and R&D competitions. I provide a full characterization of equilibria in dynamic common-value contests and use it to study their properties, including comparative statics, earlier-mover advantage, and large contests. I show that information about other players' efforts plays an important role in determining the total effort and that the total effort is strictly increasing with the information that becomes available.