IMPORTANCE: Patent foramen ovale (PFO) closure decreases recurrent stroke but increases atrial fibrillation (AF). Careful selection of patients in whom PFO is more likely to be the cause of stroke may improve outcomes by avoiding closure in patients unlikely to benefit. OBJECTIVE: To determine whether the PFO-Associated Stroke Causal Likelihood (PASCAL) classification system identifies who will experience net benefit and net harm from PFO closure. DESIGN, SETTING, AND PARTICIPANTS: This meta-analysis was a secondary analysis of individual participant-level data from the Systematic, Collaborative, PFO Closure Evaluation (SCOPE) consortium meta-analysis, including all 6 randomized trials of transcatheter PFO closure vs antithrombotic therapy alone. Participants were young and middle-aged adults (mean [SD] age, 45 [10] years) with a PFO and an otherwise cryptogenic stroke. The trials were conducted in hospitals in North America, Europe, Australia, Brazil, and South Korea from 2000 to 2017. The current analysis, involving all trial participants, was performed from January to August 2025. INTERVENTIONS: Transcatheter PFO closure plus antithrombotic therapy vs antithrombotic therapy alone. MAIN OUTCOMES AND MEASURES: The primary efficacy end point was recurrent ischemic stroke. The primary safety end point was first-ever detection of AF beyond the periprocedural period (>45 days after randomization). RESULTS: The 6 trials enrolled 3740 patients (1889 who had PFO closure, 1851 who had medical therapy); 2058 patients (55.0%) were male, and 1682 (45.0%) were female. Among patients in all 6 trials, PASCAL classified PFO relatedness to the index stroke as probable in 1382 patients (37.0%), possible in 1811 (48.4%), and unlikely in 547 (14.6%); among the 2967 patients in the 4 trials with broad entry criteria, PASCAL classified PFO relatedness as probable in 860 patients (29.0%), possible in 1565 (52.7%), and unlikely in 543 (18.3%). The reduction in the absolute rate of recurrent ischemic strokes over 5 years was greater than the increase in first-ever detection of AF in the postperiprocedural period as follows: in the probable group, fewer strokes, -2.5% (95% CI, -4.2% to -1.3%) vs more late AF, 1.3% (95% CI, 0.0% to 2.5%), and in the possible group, fewer strokes -3.4% (95% CI, -5.4% to -1.3%) vs more late AF, 1.1% (95% CI, -0.5% to 2.6%). Reduction in recurrent ischemic strokes was not observed and increase in first-ever detected postperiprocedural AF was magnified in the unlikely group (more strokes, 0.4%; 95% CI, -4.0% to 4.8%, vs more late AF, 4.6%; 95% CI, 0.3% to 8.9%). CONCLUSION AND RELEVANCE: Among young and middle-aged patients with PFO and otherwise cryptogenic stroke, the PASCAL classification algorithm distinguished the 4 of every 5 patients in the probable and possible groups with net benefit and the 1 of every 5 patients in the unlikely group with net harm from closure.