The Synergy ST (previously Labcor) valve is constructed from three separate porcine aortic cusps mounted on a scalloped, flexible, acetal copolymer stent. A group of 84 patients (31 females, 53 males; mean age 58 years; range: 19-83 years) at four centers in Brazil were studied by a single investigator at a mean of 31 months (range: 1-116 months) after implantation. There was no significant difference in peak transaortic velocity and mean gradient between the valves of different annulus size. However, effective orifice area was directly related (p = 0.0075) and resistance indirectly related to valve size (p = 0.021, ANOVA). Trivial or mild regurgitation was seen in 31 patients (37%), moderate in three (4%) and severe in two (2%). The Synergy ST porcine valve has acceptable hemodynamics of forward flow.