The increasing interest in the generation of lectin or antigen-activated (human) T cells by means of Interleukin-2 (TCGF) has led to numerous attempts to produce this substance. The simplest procedure is to use conditioned medium (CM) from IL-2 producing primary cells or cell lines with considerable activity. We describe a method of continuous CM-production in a 2-litre fermentation apparatus using a primate lymphoid cell line (MLA 144) which excretes IL-2 spontaneously. It was possible to harvest large amounts of homogeneous, lectin free material with similar production rates under different culture conditions. The activity of our CM was determined in various specific systems and proven to be comparable to that of supernatants of lectin-stimulated human primary lymphocytes.