Methods enabling the characterization of brain morphometry have evolved exponentially in the last decades and have been shown important clinical applications. First MRI studies usually included a low number of subjects, but later on, it has become recognized that efforts from different research centers can be pooled by combining data acquisition and analyses toward large-scale collaborative projects. Large-scale studies have a number of advantages, with the most intuitive being the increase in the number of enrolled subjects and, consequently, statistical power. However, there are also a number of caveats including (but not limited to) the high cost in terms of human and economic resources and the intrinsic variation of acquired data linked to the different MRI technologies. This chapter depicts the different categories of large-scale studies, according to the level of control and planning on data acquisition and analyses. It also describes the most relevant multicenter studies, from the first precursor consortia in the early 1990s to the most recent worldwide multimodal collaborative efforts.