OBJECTIVE: Aortic valve replacement (AVR) can be performed either through full median sternotomy (FS) or upper mini-sternotomy (MS). The Mini-Stern trial aimed to establish whether MS leads to quicker postoperative recovery and shorter hospital stay after first-time isolated AVR. METHODS: This pragmatic, open-label, parallel randomized controlled trial (RCT) compared MS with FS for first-time isolated AVR in 2 United Kingdom National Health Service hospitals. Primary endpoints were duration of postoperative hospital stay and the time to fitness for discharge from hospital after AVR, analyzed in the intent-to-treat population. RESULTS: In this RCT, 222 patients were recruited and randomized (n = 118 in the MS group; n = 104 in the FS group). Compared with the FS group, the MS group had a longer hospital length of stay (mean, 9.5 days vs 8.6 days) and took longer to achieve fitness for discharge home (mean, 8.5 days vs 7.5 days). Adjusting for valve type, sex, and surgeon, hazard ratios (HRs) from Cox models did not show a statistically significant effect of MS (relative to FS) on either hospital stay (HR, 0.874; 95% confidence interval [CI], 0.668-1.143; P = .3246) or time to fitness for discharge (HR, 0.907; 95% CI, 0.688-1.197; P value = .4914). During a mean follow-up of 760 days (745 days for the MS group and 777 days for the FS group), 12 patients (10%) in the MS group and 7 patients (7%) in the FS group died (HR, 1.871; 95% CI, 0.723-4.844; P = .1966). Average extra cost for MS was £1714 during the first 12 months after AVR. CONCLUSIONS: Compared with FS for AVR, MS did not result in shorter hospital stay, faster recovery, or improved survival and was not cost-effective. The MS approach is not superior to FS for performing AVR.