Cells of an antigen-specific T-cell clone, A37.4, were treated with the proteolytic enzymes trypsin or pronase to remove the T-cell antigen receptor. Removal of the receptor, analysed by surface labelling and non-reduced/reduced gel electrophoresis, stimulated the cells to synthesize new protein rapidly. New membrane protein was readily detectable within 3 h after reculture, and it was able to interact with antigen-presenting cells, since the T cells could be stimulated to produce interferon. Treatment of cells with metabolic inhibitors demonstrated that there was only a small cytoplasmic pool of protein, and de novo synthesis of mRNA was necessary for quantitative replacement of the membrane protein. The protein also required glycosylation for transport and insertion into the membrane. Despite rapid resynthesis of new receptor, when surface-labelled cells were recultured either with or without antigen-presenting cells, there was not a rapid turnover of the receptor. There was also no evidence of any loss of receptor from the membrane of antigen-stimulated cells or of any shedding of receptor into the culture medium.