Minimized perfusion circuits (MPCs) have been criticized for insufficient air elimination. The deairing capabilities of a new MPC, including an ultrasound controlled deairing unit, were compared to a standard extracorporeal circuit (ECC) in a laboratory setup. During blood flow of 4.0l/min, we injected 30-cc air over a period of 30 s into the venous line of both systems (n = 10 measurements/15-min intervals). Air was detected during the first 2 min post injection using a dual-channel ultrasound bubble counter. Venous air bubble measurements were made after the MPC bubble trap and the ECC hard-shell reservoir, respectively. Arterial air bubble data were obtained after the arterial filters (40 μm). Venous bubble count was significantly (P < 0.01) reduced in the MPC group (5–250 μm, 681 ± 177; >40 μm, 288 ± 92) compared with the ECC group (5–250 μm, 19 272 ± 682; >40 μm, 7642 ± 520). After the arterial filter, minimal numbers of air bubbles (5–250 μm, 172 ± 59; >40 μm, 0) could be detected in the MPC group, but large amounts of air (5–250 μm, 16 194 ± 1072; >40 μm, 3732 ± 997) were measured in the ECC group. The air elimination of the modern MPC is superior to conventional ECC, which may result in a reduction of neurological complications.