Background There is limited evidence whether being on fludrocortisone prevents vasovagal syncope. Objectives The authors sought to determine whether treatment with fludrocortisone reduces the proportion of patients with recurrent vasovagal syncope by at least 40%, representing a pre-specified minimal clinically important relative risk reduction. Methods The multicenter POST 2 (Prevention of Syncope Trial 2) was a randomized, placebo-controlled, double-blind trial that assessed the effects of fludrocortisone in vasovagal syncope over a 1-year treatment period. All patients had >2 syncopal spells and a Calgary Syncope Symptom Score >-3. Patients received either fludrocortisone or matching placebo at highest tolerated doses from 0.05 mg to 0.2 mg daily. The main outcome measure was the first recurrence of syncope. Results The authors randomized 210 patients (71% female, median age 30 years) with a median 15 syncopal spells over a median of 9 years equally to fludrocortisone or placebo. Of these, 96 patients had ≥1 syncope recurrences, and only 14 patients were lost to follow-up before syncope recurrence. There was a marginally nonsignificant reduction in syncope in the fludrocortisone group (hazard ratio [HR]: 0.69: 95% confidence interval [CI]: 0.46 to 1.03; p = 0.069). In a multivariable model, fludrocortisone significantly reduced the likelihood of syncope (HR: 0.63; 95% CI: 0.42 to 0.94; p = 0.024). When the analysis was restricted to outcomes after 2 weeks of dose stabilization, there was a significant benefit due to fludrocortisone (HR: 0.51; 95% CI: 0.28 to 0.89; p = 0.019). Conclusions The study did not meet its primary objective of demonstrating that fludrocortisone reduced the likelihood of vasovagal syncope by the specified risk reduction of 40%. The study demonstrated a significant effect after dose stabilization, and there were significant findings in post hoc multivariable and on-treatment analyses.