OBJECTIVE To determine the relevance of dilatations of the common femoral artery (CFA), knowledge of the normal CFA diameter is essential. The diameter of the CFA in healthy male and female subjects of different ages was investigated. METHODS The diameter of the CFA was measured in 122 healthy volunteers (59 male, 63 female; 8 to 81 years of age) with echo-tracking B-mode ultrasound scan. The influence of age, sex, height, weight, body surface area (BSA), and systolic blood pressure was analyzed by means of a multiple regression model. RESULTS The CFA increased steadily in diameter throughout life. From 25 years onwards, the diameter was larger in men than in women. Significant correlations were found between the CFA diameter and weight (r = 0.58 and r = 0.57 in male and female subjects, respectively; P <.0001), height (r = 0.49 and r = 0.54 in male and female subjects, respectively; P <.0001), and BSA (r = 0.60 and r = 0.62 in male and female subjects, respectively; P <.0001). Age and BSA were used to create a model for prediction of the CFA diameter (r = 0.71 and r = 0.77 in male and female subjects, respectively; P <.0001). CONCLUSIONS The diameter of the CFA increases with age, initially during growth but also in adults. This is related to age, body size, and sex male subjects have larger arteries than female subjects. It is now possible to predict the normal CFA diameter, and nomograms that may be used in the study of aneurysmal disease are presented.