Objective: While developed countries do age estimation for the purpose of identification, in countries such as Turkey, it is used to determine the real age of a person with an already known identity because of inaccurate birth records. The aim of this article was to investigate whether the calcification degree of the first costal cartilage could be a marker for age determination. Material and Methods: We retrospectively analyzed the postero-anterior chest x-rays of 471 patients (270 males, 201 females; mean age +/- standard deviation 42.38+/-20.69 years) who presented to the radiology department for various reasons. The calcification degree of the right first costal cartilage was classified in four stages based on criteria used by Barchilon and Garamendi, and the patients were classified in seven groups regarding their ages. The correlation between the calcification stage of the right first costal cartilages and age group was analyzed by Spearman's rho. Results: According to the first costal cartilage calcification stage, the mean ages were 5.56, 25.49, 45.39 and 66.02 at stage 0, 1, 2 and 3, respectively. The calcification degree of the right first costal cartilage and age correlated significantly in males and females [Spearman's rho=0.904, p<0.001 (0.924, p<0.001 in males and 0.864, p<0.001 in females)]. Conclusion: Although there are overlaps among age groups, the assessment of the calcification degree of the first costal cartilage on chest x-rays may be useful to predict the bone age. This age determination method can be used in criminal courts and forensic anthropology as a contributory technique.