Atopic dermatitis (AD) is a chronic, recurrent, inflammatory skin disease with an unmet need for treatments that provide rapid and high levels of skin clearance and itch improvement. To assess the safety and efficacy of upadacitinib vs dupilumab in adults with moderate-to-severe AD. Heads Up was a 24-week, head-to-head, phase 3b, multicenter, randomized, double-blinded, double-dummy, active-controlled clinical trial comparing the safety and efficacy of upadacitinib with dupilumab among 692 adults with moderate-to-severe AD who were candidates for systemic therapy. The study was conducted from February 21, 2019, to December 9, 2020, at 129 centers located in 22 countries across Europe, North and South America, Oceania, and the Asia-Pacific region. Efficacy analyses were conducted in the intent-to-treat population. Patients were randomized 1:1 and treated with oral upadacitinib, 30 mg once daily, or subcutaneous dupilumab, 300 mg every other week. The primary end point was achievement of 75% improvement in the Eczema Area and Severity Index (EASI75) at week 16. Secondary end points were percentage change from baseline in the Worst Pruritus Numerical Rating Scale (NRS) (weekly average), proportion of patients achieving EASI100 and EASI90 at week 16, percentage change from baseline in Worst Pruritus NRS at week 4, proportion of patients achieving EASI75 at week 2, percentage change from baseline in Worst Pruritus NRS (weekly average) at week 1, and Worst Pruritus NRS (weekly average) improvement of 4 points or more at week 16. End points at week 24 included EASI75, EASI90, EASI100, and improvement of 4 points or more in Worst Pruritus NRS from baseline (weekly average). Safety was assessed as treatment-emergent adverse events in all patients receiving 1 or more dose of either drug. Of 924 patients screened, 348 (183 men [52.6%]; mean [SD] age, 36.6 [14.6] years) were randomized to receive upadacitinib and 344 were randomized to receive dupilumab (194 men [56.4%]; mean [SD] age, 36.9 [14.1] years); demographic and disease characteristics were balanced among treatment groups. At week 16, 247 patients receiving upadacitinib (71.0%) and 210 patients receiving dupilumab (61.1%) achieved EASI75 (P = .006). All ranked secondary end points also demonstrated the superiority of upadacitinib vs dupilumab, including improvement in Worst Pruritus NRS as early as week 1 (mean [SE], 31.4% [1.7%] vs 8.8% [1.8%]; P < .001), achievement of EASI75 as early as week 2 (152 [43.7%] vs 60 [17.4%]; P < .001), and achievement of EASI100 at week 16 (97 [27.9%] vs 26 [7.6%]; P < .001). Rates of serious infection, eczema herpeticum, herpes zoster, and laboratory-related adverse events were higher for patients who received upadacitinib, whereas rates of conjunctivitis and injection-site reactions were higher for patients who received dupilumab. During 16 weeks of treatment, upadacitinib demonstrated superior efficacy vs dupilumab in patients with moderate-to-severe AD, with no new safety signals. ClinicalTrials.gov Identifier: NCT03738397.