Chemokines, i.e., low-molecular-weight chemotactic cytokines, are generally produced in very small amounts. Hence, liters of conditioned medium from primary cells or cell lines are necessary as start material to obtain microgram amounts of natural chemokine (see Note 1 ). A substantial quantity of a particular chemokine is only produced by certain cell types, providing that the cells are stimulated with an appropriate endogenous (cytokine) or exogenous (viral, bacterial, or plant products) inducer. Thus, if a specific immunological or biological assay is available, it is recommended to determine the optimal combination of cell type and inducer, as well as the timepoint of maximal production of the chemokine, prior to large-scale production. Maximal production of chemokines is often reached 48–72 h after addition of the inducer.