Recently, flexible fluted small silicone drains have been used widely as chest drains after cardiac surgery. Despite the clinical advantages of using smaller silastic chest drains over conventional chest tubes, an experimental comparison of the drainage capacity between these two drain tubes has not yet been performed. The drainage capacity of 19F silicone drains and 28F conventional tubes was tested. In an in vitro study, both tubes were set in a water bath and drained at a pressure of 10 mm Hg. In an in vivo study, the drains were inserted into the hemithorax in 8 adult pigs. Blood was infused at 20 mL x min(-1) into both chest cavities and the tubes were drained at 15 cm H(2)O for 30 min. In the in vitro study, the drainage capacity of the conventional chest tube was 9-times higher than that of the smaller silicone drain (103.8 vs. 11.6 L x hr (-1)). However, in the in vivo study, there was no difference in drainage capacity between the two different tubes over time. This experiment demonstrated that the smaller silastic chest drain has sufficient drainage capacity, almost identical to the conventional chest tube, in the clinical setting.