In order to develop a "half-way" venous catheter for clinical use, anthropometric (n = 200), radiographic (n = 101), and phlebographic (n = 44) investigations were undertaken to determine the lengths, diameters, and morphology of the basilic and cephalic veins from fossa cubiti to the lateral edge of the first rib. The lengths of basilic and cephalic veins varied from 25 to 45 cm, exceeding 40 cm in approximately 5% of cases. Catheter lengths to be inserted were correlated ("r" = 0.6-0.7) with body heights, accurately estimated by 1/5 of the body height (cm) plus 2 cm for the basilic vein, and 4 cm for the cephalic vein. The cephalic veins have small proximal end diameters (mean = 6 mm), and present terminal arches of 2-3 cm. These are connected by a rich anastomotic network to the superficial cervical veins. The basilico-axillary courses are regular with gradually increasing diameters (mean = 16 mm), but in some observations, with the arms maximally abducted, the axillary veins presented accentuated folds. With these considerations, we recommend the insertion of the "half-way" catheters by basilic approach with the patient's arm in 90 degree abduction. The axillosubclavian length (mean = 18.5 cm) ensures wide limits for accurate placement of the "half-way" catheter tips when a basilic approach is used. Further, their large diameters (16-19 mm) make flotation of the soft catheters probable.