The phenotype of intestinal intraepithelial lymphocytes (IEL) of young calves has not been described. In order to determine the potential role of IEL in protection against enteric infection, it is important to characterize these cells in normal calves. Therefore, IEL of calves were analyzed phenotypically and compared with peripheral blood lymphocytes (PBL) via flow cytometry using monoclonal antibodies to cell surface markers. Approximately 25% of PBL and IEL expressed the gamma/delta T-cell receptor (TCR-1+). TCR-1+ PBL co-expressed WC1 (antigen expressed on a subset of lymphocytes expressing the gamma/delta T-cell receptor), whereas only a small percent of TCR-1+ IEL co-expressed WC1. TCR-1+ cells in the PBL co-expressed the interleukin-2 receptor (IL-2r), whereas TCR1+ cells in the IEL co-expressed ACT-2 (null cell and CD-8+ T-cell activation marker). There were approximately twice as many CD-4+ cells as CD-8+ cells in the PBL, whereas there were three to five times as many CD-8+ cells as CD-4+ cells in the IEL. Thus, IEL of calves are antigenically distinct from PBL.