Introduction <p>Hyaluronic acid (HA) is widely used for facial rejuvenation and soft tissue volumization, with lip augmentation being one of its primary applications. The rheological properties of HA fillers are essential to ensure the efficacy and safety of procedures, directly influencing the aesthetic outcome and material longevity.</p> Objective <p>This study aims to evaluate the rheological properties of three hyaluronic acid-based fillers indicated for lip volumization: Belotero Intense (Merz), Kysse (Galderma), and Volift (Allergan).</p> Methods <p>Twenty-four syringes of fillers were analyzed, with 8 samples from each brand. The rheological properties investigated included storage modulus (G'), loss modulus (G''), complex modulus (G*), phase angle (Tan(delta)), and cohesiveness. Measurements were conducted using the Kinexus PRO rheometer with parallel plate geometry.</p> Results <p>The results revealed significant differences among the three fillers. Volift exhibited higher resistance to deformation, reflected by the higher G* values, while Kysse stood out for its greater cohesiveness.</p> Conclusion <p>These rheological variations suggest that each filler may be more suitable for different clinical applications, such as lip augmentation or deeper tissue filling.</p> Level of Evidence V <p>This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors <a href="http://www.springer.com/00266">www.springer.com/00266</a>.</p>