T-cell diversity is multifactorial and includes variability in antigen specificity, differentiation, function, and cell-trafficking potential. Spectral overlap limits the ability of traditional flow cytometry to fully capture the diversity of T-cell subsets and function. The development of mass cytometry permits deep immunoprofiling of T-cell subsets, activation state, and function simultaneously from even small volumes of blood. This chapter describes our methods for mass cytometry and high-throughput data analysis of T cells in patient cohorts. We provide a pipeline that includes practical considerations when customizing a panel for mass cytometry. We also provide protocols for the conjugation and titration of metal-labeled antibodies (including two T-cell panels) and a staining procedure. Finally, with the aim to support translational science, we provide R scripts that contain a detailed workflow for initial evaluation of high-dimensional data generated from cohorts of patients.