Abstract: Analogs of SRIF which are selective for SSTR1 in contrast to the other cloned SRIF receptors. These analogs are useful in determining the tissue and cellular expression of the receptor SSTR1 and its biological role in the endocrine, exocrine and nervous system, as well as in regulating tumor growth. SRIF analog peptides, such as des-AA1,2,5[D-Trp8, N?MeIAmp9, Tyr11]-SRIF and counterparts incorporating Cbm at the N-terminus and/or N?Ser13, inhibit the binding of a universal SRIF radioligand to the cloned human receptor SSTR1, but they do not bind with significant affinity to human SSTR2, SSTR3, SSTR4 or SSTR5. By incorporating an iodinated tyrosine in position-2 or in position-11 in these SSTR1-selective SRIF analogs, a labeled compound useful in drug-screening methods is provided. The N-terminus accommodates bulky moieties without loss of selectivity, and a carbamoyl moiety or a conjugating agent that will accept a radioactive nuclide or will link to a cytotoxin may be present at the N-terminus.