Exosomes are membrane nanovesicles (approximately <120 nm in size) released by most, if not all, living cells and in particular by leukocytes. They originate within the endocytic compartment by invagination of the endosome membrane. Therefore, they have a different biogenesis and molecular composition than microvesicles (>0.2 μm) shed from the plasma membrane. Although the functions of exosomes in vivo are beginning to be elucidated, increasing evidence suggests that exosomes constitute a mechanism of cell-to-cell communication, transferring antigens, proteins, mRNAs, and noncoding RNAs among cells. Interestingly, effector T cells including cytotoxic T lymphocytes (CTLs) release death-inducing molecules of the TNF superfamily through exosomes contained in their cytotoxic granules. The present chapter provides basic protocols for purification of exosomes secreted by CTLs.