Long-term follow-up data following 2 breast enhancement treatments with stabilized hyaluronic acid (HA) gel are limited. Although HA gel is no longer marketed for breast enhancement, there is a clinical need for information about follow-up of previously treated women. A multicenter, noncomparative study was conducted in women seeking breast enhancement. Subjects received 1 treatment of HA gel (maximum, 100 mL/breast); a subgroup underwent retreatment 9 months later. Follow-up was conducted for 24 months after last treatment; endpoints included magnetic resonance imaging for estimation of gel degradation, adverse events, breast examinations, Global Esthetic Improvement Scale, and satisfaction ratings. Seventy-one subjects received 1 treatment, with 22 (31%) receiving retreatment after 9 months. Twenty-four months after last treatment, the mean percentage of remaining gel was 17% in the single-treatment group and 21% in the retreatment group; complete degradation had not occurred in any subject. The most commonly reported treatment-related adverse events were implant-site nodules, medical device implantation events, capsular contracture associated with breast implant, and injection-site nodules; most were mild to moderate and required no intervention. Based on subject Global Esthetic Improvement Scale ratings, 36% of breasts in the single- treatment group and 50% of breasts in the retreatment group were improved 24 months after last treatment, but subject satisfaction had returned to baseline levels. Some gel remained in all subjects 24 months after last treatment. Although single treatment and retreatment were generally well tolerated, physicians need to be aware of common treatment-related complications to manage them adequately.