Abstract The histamine H 1-receptor-like binding sites in the nervous tissue of the locust Locusta migratoria were investigated with a conventional radio-receptor assay using [ 3H]mianserin as the radio ligand. Binding of [ 3H]mianserin to the binding site is sensitive to proteases and heat treatment. It shows the characteristics of ligand-receptor interactions. The single binding site has high affinity for mianserin (K D = 7.05 nM) and is present in high concentrations (B max = 1.53 pmol/mg) in the whole nervous tissue. All tested antihistamines have a high affinity for the binding site, which suggests that it represents an insect histamine receptor. Nevertheless, it shows its peculiarities distinguishing it from vertebrate histamine H 1-receptors.