Antigen pulsed antigen presenting cells (APCs) were fixed to a carrier (culture flask or microtiter plate) to stimulate antigen-specific T cell clones in vitro. The resulting stimulation was comparable with that in which free antigen together with irradiated APCs were used and the antigen concentration was less critical in the case of toxic antigens. It was shown that the carriers coated with pulsed APCs could be stored for 12 weeks without loss of stimulatory capacities, provided that the APCs were fixed. In addition it was demonstrated that coated carriers could be used thrice stimulate T cells in vitro without affecting the stimulating properties. The observed T cell proliferation was both antigen specific and MHC restricted. The main advantages of this novel method were the standardization of antigen stimulation of T cells achieved in vitro and the availability of a 100% pure T cell population immediately after stimulation, both features contributing to more reproducible experiments with T cell clones or lines in vivo and in vitro.