Aims: To evaluate the outcome of surgical treatment of benign and aggressive chondroblastoma in the Prague bone tumours register. Methods: Between 1969–2001 57 patients (38 men and 19 women) with chondroblastoma have been registered. The age ranged from 7 to 52 years – in average 19 years. The most frequent localizations were epiphyses of long bones (13 proximal humerus, 10 proximal femur, distal femur and proximal tibia each 11). We also observed atypical localizations (3 patella, 2 pelvis and 1 each in, fibula, talus, 5th metatarsal). All patients had available x-rays for evaluation and some arteriography or CT. All had histological verification. The treatment of choice was intralesional curetting and filling with auto or allografts. The femoral head lesions were treated through an original femoral neck approach to prevent hip luxation. We registered 5 aggressive variants with a different clinical course. They recur after intralesional surgery, are purely osteolytic and richly vascularized. One patient even developed lung metastasis. Results: In the usual type of benign chondroblastoma all patients were healed after intralesional surgery and graft filling with well-preserved function. In the aggressive form we performed a limb saving reconstructive surgery (knee arthrodesis, total knee or hip endoprosthesis). Conclusions: For benign chondroblastoma intra-lesional surgery brings excellent results. The aggressive form should be differentiated and resected at least marginally without delay to prevent larger skeletal defects.