Lymphoid cells of the dark agouti (AgB 4 or Rt H1.1) rat were extracted with 3M KCl. This soluble extract was shown by inhibition of specific, cytotoxic alloantisera to contain the private antigen, AgB 4, and the public antigens, AgB 26, 30 and 29. The public antigens AgB 27 and 28 were not assayed. A species-specific antigen and a non-AgB antigen were also present. Equal concentrations of the various antigens were not obtained. Gel filtration of this extract over Sephadex G-200 yielded AgB 4,26, and 30 and the species antigen at the front of the inner bed volume with a minor AgB 4 peak at about 65,000 mol. wt. AgB 29 and the non-AgB antigen were not recovered. As AgB 29 was present in high concentration in the extract and shown not to be highly labile, it is suggested that it may be present on a molecule distinct from that carrying AgB 4,26 and 30.