Anoxia causes severe damage in neuronal cells, whereas its influence on neural stem cells (NSC) is less investigated. We have investigated the influence of anoxia on NSC proliferation and survival. Additionally we tested effects of Erythropoietin (EPO), a neuroprotective cytokine. We cultured NSC from hippocampus, olfactory bulb and subventricular zone of adult rat brains to expose them to normoxia (controls) or anoxia (5 % CO2 in N2) for 24 hrs. EPO concentrations ranged from 0.1 to 100 u/ml. Cell viability was measured using CellTiter 96 AQueousOne (Promega, Mannheim). NSC showed increased cell numbers during anoxia by 10–13 % (bulbus), 8-9 % (subventricular zone) and 3–7 % (hippocampus) (n=240 p<0.01 each) compared to controls. No EPO effect on viability was detected in normoxia and anoxia (n.s.). Caspase activity was determined using Apo-ONE Homogenous Caspase-3/7 Assay (Promega). Caspase activity of anoxic cells was increased more than 2.2-fold (n=18 p<0.01), but no EPO effects were visible (n=18 n.s.). It is concluded that anoxia induces proliferation of NSC in spite of increased apoptosis whereas EPO shows no short term effect in this context. Support: BMBF: NGFN 2.