INTRODUCTIONChondroblastoma (CB) is a rare, benign, cartilaginous lesion of the bones that accounts for less than 1% of primary bone tumours.(1,2) It typically develops from the epiphysis of skeletally immature patients. (3,4) Peak incidence of CB is seen in the second decade of life, (5,6) and has been reported to occur more frequently in men than in women. (5,(7)(8)(9)(10) Although CB has a predilection for tubular bones such as the humerus, femur, tibia and metatarsus, (7,11) it can also be found in non-tubular bones (NTBs) such as flat bones (i.e. skull, maxilla and pelvis) (7) and epiphysoid bones (i.e. trapezium, (12) cuboid, (13,14) talus (15,16) and patella (17) ).Multifocal benign CB has also been reported. METHODSThis study was approved by the ethics committee at the Ramathibodi Hospital, Bangkok, Thailand (ID-10-52-01). We retrospectively reviewed the medical records of all patients with pathologically proven CB at our hospital during a 37-year period . A total of 31 patients (16 men; 15 women)