This paper reviews recent empirical studies of location and innovation. The objective is to highlight the questions addressed, approaches adopted, and further issues that remain. The review is organized around the traditions of measuring geographically mediated spillovers and productivity studies that introduce a geographic dimension. The first part identilies four separate strains in thc empirical spillover literature: innovation production functions; the linkages between patent citations. defined as paper trails: the rnobility of skilled labor based on the notion that knowledge spillovers are transmitted through people; and, last, knowledge spillovers embodied in traded goods. The second part considers the composition of agglomeration economies, the attributes of knowlcdge, and the characteristics of firms.