The F-11 cell line is a fusion product of embryonic rat dorsal root ganglion (DRG) cells with mouse neuroblastoma cell line N18TG-2 (Platika, D., Boulos, M.H., Baizer, L. and Fishman, M.C., Proc. Natl. Acad. Sci. U.S.A., 82 (1985) 3499-3503). F-11 cells were uniformly labelled using a monoclonal antibody (RT-97) to the 200 kDa subunit of neurofilament protein, which labels a subpopulation of adult rat DRG neurons. F-11 cells did not stain for antigenic markers of fibroblasts or Schwann/satellite cells which are also present in DRG. Monoclonal antibodies that recognize cell surface carbohydrates have been shown to label subpopulations of DRG neurons. The stage-specific embryonic antigens SSEA-3 and SSEA-4, and the antigen recognized by B23D8, were expressed by some F-11 cells but not by the neuroblastoma parent of the hybrid cells. SSEA-3 was expressed by about 20% of the F-11 cells, whereas 40-60% expressed SSEA-4 or the antigen recognized by B23D8. The stability of F-11 cell subpopulations for sensory antigen expression was demonstrated by isolating single cells and growing the progeny as clonal lines. In some subclones, nearly 100% of the cells stably expressed SSEA-4 and/or B23D8, or failed to stain with anti-SSEA-4, anti-SSEA-3, or B23D8 over 12 passages. Other subclones were unstable for the expression of these antigens. This study demonstrates the derivation of the F-11 cell line from sensory neurons but also indicates that multiple phenotypes of varying stability are present in this line. This information is important for the use of this line as a model for DRG neurons.