Echocardiographic determination of prosthetic valve effective orifice area has become generally accepted, although many differing methodologies are used. The use of the continuity equation employing the velocity-time integrals has been established as accurate, but another method using the more easily measured peak velocities has also been employed. This study compares these two methods using data from a multicenter, prosthetic valve trial that is single-observer reviewed. The results showed that the two methods do not give the same result in this prosthetic valve.