Treatment of high blood pressure with antihyper- tensive medication is recommended to prevent ische- mic stroke, intracerebral hemorrhage, and cardiac, renal, and other end-organ injury (Class I; Level of Evidence A). 2. Hypertension should be treated, and such treatment may reduce the risk of aSAH (Class I; Level of Evidence B). 3. Tobacco use and alcohol misuse should be avoided to reduce the risk of aSAH (Class I; Level of Evidence B). Table 2. Definition of Classes and Levels of Evidence Used in AHA Stroke Council Recommendations Class I Conditions for which there is evidence for and/or general agreement that the procedure or treatment is useful and effective. Class II Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment. Class IIa The weight of evidence or opinion is in favor of the procedure or treatment. Class IIb Usefulness/efficacy is less well established by evidence or opinion. Class III Conditions for which there is evidence and/or general agreement that the procedure or treatment is not useful/effective and in some cases may be harmful. Therapeutic recommendations Level of Evidence A Data derived from multiple randomized clinical trials or meta-analyses Level of Evidence B Data derived from a single randomized trial or nonrandomized studies Level of Evidence C Consensus opinion of experts, case studies, or standard of care Diagnostic recommendations Level of Evidence A Data derived from multiple prospective cohort studies using a reference standard applied by a masked evaluator Level of Evidence B Data derived from a single grade A study, or 1 case-control studies, or studies using a reference standard applied by an unmasked evaluator Level of Evidence C Consensus opinion of experts 4. 