The striatum is a heterogeneous brain structure with microstructural gradients along its main axes. Changes in its organization are associated with normal aging and disease. Yet the spatial variability in the human striatum is not well characterized and is mostly limited to postmortem studies. We propose a robust non-invasive method for detection and quantification of microstructural gradients along axes of the striatum in individuals in vivo, using qMRI. We show distinct profiles of spatial and aging-related changes in the striatum, associated with different biophysical sources such as tissue density and iron content, estimated in vivo.