In the gerbil hippocampus activated microglial antigens are intensely stained by cerebrospinal fluid from patients with Alzheimer's disease (AD-CSF), OX18 and the amyloid precursor protein (beta-APP) up to 14 days after ischaemia. Propentosylline (PPF), which facilitates the adenosine A2 receptor action, has been shown to be neuroprotective, to depress O2- radical formation in macrophages and to interfere with the generation of phagocytotic macrophages from cultivated microglial cells. In this report we tested in ischaemic gerbils whether PPF treatment influences the potential neurotoxic properties of microglia. Daily post-treatment with PPF, started 24 h after ischaemia, depressed the immunostaining of activated microglia by AD-CSF, OX18 and APP in the hippocampus. Thus, PPF may protect against microglia-related brain damage.