This chapter provides a comprehensive review of the imaging characteristics of permanent synthetic fillers in the gluteal region, primarily focusing on liquid silicone and polymethyl methacrylate (PMMA). Magnetic resonance imaging (MRI) is emphasized as the preferred diagnostic modality, capable of evaluating filler distribution, complications, and post-surgical outcomes. It includes detailed descriptions of filler appearance in high versus low proton-density materials and introduces concepts like “noodle images” for muscle infiltration. Migration patterns, particularly ascending, are explained in anatomical and clinical contexts. The chapter also discusses computed tomography (CT) and ultrasound’s complementary and limited roles in this region.