Summary. Development of mini invasive techniques for implantation of unicondylar knee prostheses has increased general interest in this type of surgery. Indications are single compartment arthrosis, patients over 50 years of age with total body weight of less then 80 kg with small axis deviations and ligaments preserved. Important contraindications are systemic diseases. Authors present mid term postoperative results for 25 patients and 26 knees after implantation of unicondylar knee prosthesis type Repicci. Average age at time of surgery was 64.3, predominantly women and in all patients varus deformity with medial compartment arthrosis was seen. According to the Ahlback classification patients were from type 1 to type 4. Average follow up was 31.8 months. We achieved good axial correction with femorotibial angle of 6.2 degrees postoperatively, with flexion of 118 degrees and only in 3 knees extension lag was seen of an average of 8.3 degrees. According to the Knee Society Questionnaire, knee score was 60 points preoperatively and 86.8 points postoperatively and functional score was 30.9 points preoperatively and 71.1 points postoperatively. Pain level, according to the Visual Analogue Scale, was preoperatively 6.8 points and 2 points postoperatively (10 was max). We conclude that the unicondylar knee arthroplasty is a good solution for patients with early degenerative changes in one knee compartment. This type of operative procedure will be more used because of numerous advantages when compared to other treatment options.