Poly(A)-positive mRNA extracted from tonsillar mononuclear cells stimulated with phytohemagglutinin-M and 12-o-tetradecanoyl phorbol 13-acetate was successfully translated into biologically active interleukin 2 (IL-2) in Xenopus laevis oocytes, and secreted into the incubation medium. In control experiments, the extract of oocytes injected with either poly(A)-negative RNA or buffer did not show any IL-2 activity. By sucrose density gradient centrifugation analysis, IL-2 mRNA was found as a single peak corresponding to a sedimentation coefficient of 10-11S.