Stilbazulenyl nitrone (STAZN) is a potent antioxidant that, in a rat model of transient focal cerebral ischemia, confers significant enduring functional and morphological neuroprotection. This study investigated the influence of dose and time of administration on the neuroprotective effects of STAZN in the intraluminal suture model of middle cerebral artery occlusion (MCAo). Dose response: At 2 and 4 h after the onset of MCAo, animals received intravenously either STAZN (low dose=0.07 mg/kg, n=8; medium dose=0.7 mg/kg, n=9; high dose=3.5 mg/kg, n=9), an equivalent volume of vehicle (30% Solutol HS15 and 70% isotonic saline, 0.37 ml/kg, n=5) or saline (0.37 ml/kg, n=5). Only the medium dose improved scores (p<0.05) on a standardized neurobehavioral test at 1, 2 and 3 days after MCAo. Only the medium dose reduced the total infarction (51%, p=0.014) compared to controls. These results indicate that STAZN exhibits maximal neuroprotection at the 0.7 mg/kg dose. Therapeutic window: STAZN (0.6 mg/kg) dissolved in dimethylsulfoxide was given intra-peritoneally at 2 and 4 h (n=11), 3 and 5 h (n=10), 4 and 6 h (n=10) or 5 and 7 h (n=7) after the onset of MCAo. Additional doses were given at 24 and 48 h. Vehicle (dimethylsulfoxide, 2.0 ml/kg, n=6) was administered at 3, 5, 24 and 48 h. STAZN treatment initiated at 2 or 3 h after the onset of MCAo improved neurological scores (p<0.001) and reduced total infarction (42.2%, p<0.05) compared to controls.