The superficial temporal artery to middle cerebral artery (STA-MCA) bypass is the most common bypass for augmenting or restoring cerebral blood flow. Although the single-barrel (SB) STA-MCA bypass is sufficient in most cases, the double-barrel (DB) STA-MCA bypass can supply the demands of different vascular territories or multiple efferent arteries. We present a comparative analysis of SB and DB STA-MCA bypass in a large, consecutive series to examine indications, surgical results, and patient outcomes. A retrospective review of a prospectively maintained database identified all STA-MCA bypasses performed by a single surgeon over 21 years. In total, 261 patients received 378 STA-MCA bypasses in 351 surgeries. SB STA-MCA bypasses were performed in 234 patients (90%), whereas DB STA-MCA bypasses were performed in 27 patients (10%). Patients with DB STA-MCA bypasses were more likely to undergo bilateral bypass procedures than those receiving SB STA-MCA bypass (P < 0.0001). In patients with bilateral STA-MCA bypasses (n= 91, 35%), 69 patients received bilateral SB STA-MCA bypasses (76%), whereas 22 patients received a DB STA-MCA bypass on 1 hemisphere (24%). There was no difference in bypass patency or clinical outcome in patients with SB and DB STA-MCA bypasses. DB STA-MCA bypasses are reserved for patients requiring revascularization of multiple vascular territories or efferent arteries. DB STA-MCA bypasses have patency rates and patient outcomes comparable to SB STA-MCA, with the advantages of a single incision and reduced operative complexity compared to high-flow bypasses. DB STA-MCA bypass is an important element in the vascular neurosurgeon's bypass armamentarium.