The assignment of a large number of resonances in the 300‐MHz 1H‐nmr spectrum of the polypeptide neurotoxin Anemonia sulcata toxin I is described. The initial identification of spin systems is made using both one‐ and two‐dimensional nmr spectra. The subsequent assignment of these spin systems to specific residues in the molecule is based largely on the observation in two‐dimensional spectra of through‐space connectivities between Hα and NH resonances from adjacent residues in the amino acid sequence. Using these techniques, the full spin systems of 22 residues are specifically assigned, together with partial assignments for a further 8. Many of the spin systems from the remaining 16 residues have been defined, although not yet specifically assigned. From the pattern of through‐space connectivities between protons from adjacent residues in the sequence, some inferences may be drawn concerning the secondary structure of this polypeptide in aqueous solution.