BACKGROUND Tuberculosis is an essential problem for healthcare systems especially in developing countries. All newborns are given Bacillus Calmette-Guérin (BCG) vaccine in Iran which is prepared from live bovine tuberculosis bacillus, and is given to protect against tuberculosis. Osteomyelitis secondary to BCG vaccination is rare and usually involves epiphysis of long tubular bones. METHODS 4 patients, 3 males and a female entered this study and were between 11 to 24 months old. The involved bones were first metatarsi, talus, humerus and tibia bone. The main radiologic finding was lytic lesion with cortical destruction and periosteal reaction. RESULTS 3 patients underwent core needle biopsy and the one with the proximal tibia involvement, underwent open surgery. Pathology report suggested granulomatous osteomyelitis and typical caseous necrosis compatible with tuberculosis. Surgical treatment for these patients was curettage and debridement of the bone lesion and involved tissues around. The patients got standard anti TB pharmacotherapy, were completely cured and no short term complication was seen in a one year follow up. CONCLUSIONS BCG osteomyelitis and cold abscess, should be kept in mind when assessing a child presenting chronic symptoms like pain, limping or local swelling of extremities. The long interval time between BCG vaccination and outbreak of the culture-negative abscess is a major point which emphasizes on pathologic evaluation. Image guided tissue biopsy and PCR studies confirm diagnosis. Early use of a surgical curettage and debridement along with chemotherapy soon afterwards, enabled these children to enjoy a satisfactory clinical outcome.