Established cell lines derived from human malignant astrocytomas typically express a combination of platelet‐derived growth factor (PDGF) and PDGF receptor which could form an autocrine loop. In this study, we screened for the essential components of a PDGF autocrine loop in fresh surgical isolates of human astrocytomas, using in situ hybridization and immunohis‐tochemical techniques. Eight malignant astrocytomas (6 glioblastomas and 2 anaplastic astrocytomas), 5 low‐grade astrocytomas and 4 non‐neoplastic glial specimens (mesial temporal sclerosis) were evaluated. Malignant astrocytomas, and to a lesser extent low‐grade astrocytomas, expressed more PDGF‐A and PDGF‐B than non‐neoplastic glia. PDGF‐α‐receptor expression was elevated both in malignant and in iow‐grade astrocytomas. These data support the argument that PDGF autocrine loops contribute to the unregulated growth of human astrocytomas. Expression of PDGF and PDGF receptor in low‐grade astrocytomas suggests that activation of PDGF autocrine loops may be an early event in the pathogenesis of malignant astrocytomas. © 1995 Wiley‐Liss, Inc.