To evaluate the role of gamma knife stereotactic radiosurgery (SRS) in the management of newly diagnosed (early) or progressive (delayed) WHO grade II astrocytomas, the authors reviewed 25 patients who underwent SRS for pathologically proven WHO grade II astrocytomas between 1987 and 2009 at the University of Pittsburgh. The median patient age was 30 years (range 8-68 years). Sixteen patients had early SRS after stereotactic biopsy (n = 14), resection (n = 1) or radiation therapy (n = 1), and 9 underwent delayed SRS for progression after surgical resection (n = 3), radiation therapy (n = 4) or both (n = 2). The median tumor volume was 3.7 cm(3) (range 0.6-17.0 cm(3)) and the median margin dose was 14 Gy (range 11-20 Gy). At a median of 65 months of follow-up (range 6-208 months), tumor control was observed in 13 patients (52%). The progression-free survival rates after SRS at 1, 5 and 10 years were 91.3, 54.1 and 37.1%, respectively. On both univariate and multivariate analysis smaller tumor volume (<6 cm(3)), higher marginal dose (≥15 Gy) and absence of contrast enhancement on imaging studies were associated with better progression free-survival. Gamma knife SRS is an additional option for patients with small volume, deep seated, non-enhancing and well-demarcated WHO grade II astrocytomas and does not preclude later conventional fractionated radiation therapy, cyst aspiration, or cautious debulking if feasible. It may also benefit patients with residual or recurrent tumors that have progressed after surgery, radiation therapy or both.