[en] Human brain tumors and nude mouse-borne human neuroblastomas and gliomas were analyzed for sigma and opioid receptor content. Sigma binding was assessed using [³H] 1, 3-di-o-tolylguanidine (DTG), whereas opioid receptor subtypes were measured with tritiated forms of the following: μ, [D-ala², mePhe⁴, gly-ol⁵] enkephalin (DAMGE); κ, ethylketocyclazocine (EKC) or U69,593; δ, [D-pen², D-pen⁵] enkephalin (DPDPE) or [D-ala², D-leu⁵] enkephalin (DADLE) with μ suppressor present. Binding parameters were estimated by homologous displacement assays followed by analysis using the LIGAND program. Sigma binding was detected in 15 of 16 tumors examined with very high levels found in a brain metastasis from an adenocarcinoma of lung and a human neuroblastoma (SK-N-MC) passaged in nude mice. κ opioid receptor binding was detected in 4 of 4 glioblastoma multiforme specimens and 2 of 2 human astrocytoma cell lines tested but not in the other brain tumors analyzed