The study aimed to Compare the effect of combination Platelet Rich Plasma with bovine derived xenograft and bovine derived xenograft alone in treatment of human class II furcation defects in mandibular molars. Twenty systemically healthy patients, aged 32 to 58 years with chronic periodontitis participated in the study . Each patient had 2 buccal mandibular class II furcation defects (first or second molars) were randomizely treated either with : bovine – derived xenograft with Platelet – Rich plasma, or with bovine - derived xenograft alone.