BACKGROUND AND PURPOSE Elevated blood pressure (BP) is associated with greater severity of intracranial atherosclerotic stenosis (ICAS) and increased risk of ischemic stroke. Because little is known about the relationship of maintained BP level with progression of symptomatic ICAS (sICAS), we evaluated the independent association of maintained systolic BP (SBP) with risk of sICAS progression. METHODS We analyzed the Trial of cilOstazol in Symptomatic intracranial Stenosis 2, which evaluated 402 stroke patients with sICAS (mean age, 64.5±11.3 years; male, 52.2%). Study participants were categorized into four groups according to mean SBP level: low-normal (<120 mm Hg), normal to high-normal (120 to 139 mm Hg), high (140 to 159 mm Hg), and very-high (≥160 mm Hg). Progression of sICAS was defined as worsening in the degree of stenosis by ≥1 grade on the 7-month magnetic resonance angiography follow-up. RESULTS sICAS progression was observed in 52 (12.9%) subjects. Percentages of sICAS progression by mean SBP category showed a J-shape pattern: low-normal (21.4%), normal to high-normal (10.7%), high (11.4%), and very-high (38.9%). In multivariable analysis, compared to the normal to high-normal SBP group, odds ratios (95% confidence intervals) were low-normal, 1.88 (0.62-5.67); high, 1.06 (0.47-2.37); and very-high, 8.75 (2.57-29.86). Rate of sICAS progression by 10-mm Hg strata showed a similar pattern to findings from mean SBP category (9.47; 2.58-34.73 for SBP ≥160 mm Hg). CONCLUSIONS Among individuals with a recent ICAS stroke, very-high SBP level during the short-term period after the index stroke was associated with significantly greater odds of sICAS progression.