This study, carried out in pig caudate membranes, characterises the radioligand binding site labelled with [3H]L-694,247 (2-[5-[3-(4-methylsulphonylamino)benzyl-1,2,4-oxadiazol-5-yl ]-1H-indole-3 - yl]ethylamine). The affinities of 27 standard compounds are consistent with binding to a 5-HT1D recognition site. In addition the results indicate that, under the assay conditions described, [3H]L-694,247 specifically labels the 5-HT1D beta recognition site since ketanserin and ritanserin display a low affinity consistent with their activities at this subtype of the 5-HT1D receptor.