In order to generate highly labelled neurotensin analogues, synthesis has been performed of two types of precursors, one for iodination and one for tritiation. Iodination of native neurotensin occurs on both tyrosines in position 3 and 11 and thus affects greatly its binding capacities. In this article, synthesis and chemical characterization of [Trp11]-neurotensin are described which can be iodinated without loss of activity. Synthesis was by solid phase procedure on an experimental support, Pab-resin, alpha-(4-chloromethylphenylacetamido)-benzyl copoly (styrene 1 per cent divinylbenzene). After esterification of Boc-Leu by its cesium salt on the Pab-resin, each amino acid was incorporated by a double coupling with dicyclohexylcarbodiimide on a Beckman 990 synthesizer. The trifunctionnal amino acids were protected as follows : Tyr as the 2,6-dichlorobenzyl ether, Glu as benzyl ester, Lys by the benzyloxycarbonyl group, Arg by the tosyl group, and Trp by the formyl group. Boc-Asn was incorporated by the HOBt procedure. The cleavage of peptide-resin bond and the removal of lateral chain protecting groups was realized by hydrofluoric acid with 10 per cent anisol for 1 h at 0 degrees C. The peptide obtained was then treated by NH4HCO3 1 M, pH 9, for 24 h for the removal of tryptophan formyl protecting group. Purification of the crude peptide on Bio-Gel P2 followed by ion exchange chromatography on carboxymethylcellulose (CM 52) and a final desalting on Bio-Gel P2 proved very efficient in removing several shorter contaminants.(ABSTRACT TRUNCATED AT 250 WORDS)