Efforts to elicit polyclonal antibodies to PHLIP-8 (the N-terminal octapeptide of rabbit stomach mucin is <Glu-Val-Asp-Pro-Asn-Ile-Gln-Ala-OH) have been unsuccessful; also, recent efforts to raise polyclonal antisera to bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) have met with very limited success. Our experiences, as well as those of others with TRH (<Glu-His-Pro) and tufsin (Thr-Lys-Pro-Arg), indicate that many small, physiologically important peptides are poor antigens when coupled to protein carriers using conventional techniques. As antisera to several of these peptides are required in other ongoing projects, efforts will continue to devise strategies to raise polyclonal and/or monoclonal antisera using a variety of peptide structural analogues as antigens in addition to a variety of proteins known to elicit immune system respon- siveness.