The recognition of a wide diversity of antigens by lymphocytes is made possible by the expression of a large range of highly variable antigen specific receptors, coded for by tandem arrays of genes, which undergo rearrangement during T- and B-cell development. The study of T-cell receptor (TCR) diversity and clonal composition of mixed T-cell populations has taken advantage of the features of the TCR molecule in various ways. This chapter focuses on the study of T-cells obtained from the synovial fluid of patients with inflammatory arthritis. Methods to process and store the samples and to separate cell populations are described. Two alternative molecular methods to analyse TCR diversity, identify clonal expansions, and track specific T-cell populations over both time and location are also detailed.