Objectives: Comparison of the treatment outcomes after regenerative periodontal surgery using either an enamel matrix derivative (Emdogain®) or a synthetic bone graft (Ostim®) in wide intrabony defects. Method: Twenty-four patients with chronic periodontitis were recruited at a German university dental clinic. All patients showed intrabony defects of at least 4 mm depth and 2 mm width. Using a microsurgical technique a modified papilla preservation flap was prepared. After debridement, patients were randomly assigned to Emdogain group (test) or Ostim group (control). Assessments at baseline and after 6 months included bone sounding, attachment level, probing pocket depth, bleeding on probing, and recession. Early wound healing, adverse effects and patients perceptions were also recorded. Results: Both treatment modalities led to significant clinical improvements. Change in bone fill 6 months after surgery was 1.5mm (±1.3) in the test group and 1.5mm (±1.7) in the control group, respectively. A gain in clinical attachment of 2.1mm (±1.8) in the test group and 1.7mm (±2.1) in the control group was observed. A reduction in probing pocket depth of 3.2mm (±1.4) in the test group and 2.9mm (±1.8) in the control group was recorded. One week after surgery primary closure was maintained in 100% of both the test and control groups. No differences in patients' perceptions were found. Conclusion: In both treatment procedures (Emdogain® and Ostim®) regenerative periodontal surgery in deep 1- or 2-wall intrabony defects resulted in significant clinical improvement after 6 months compared to baseline. Further investigation is needed to identify factors influencing individual responses. Keywords: regenerative periodontal surgery, chronic periodontitis, intrabony defects, bone fill