This paper reports a Genetic Algorithm (GA) based reconstruction procedure to determine the elastic constants of an orthotropic plate from ultrasonic velocity data. Phase velocity measurements are carried out using ultrasonic back-reflection technique on laminated unidirectional graphite-epoxy (0)16 and quasi-isotropic graphite-epoxy (+45, -45, 0, 90)7s fiber reinforced composite plates. A forward model to generate the slowness curves from elastic constants has been used to verify the quality of the reconstruction. The sensitivity of the chosen GA parameters is studied. As expected, out of 9 orthotropic elastic constants to be determined, the C23 and C44 found to be insensitive. The GA based reconstruction using data obtained from multiple planes were evaluated and it is shown that the single plane reconstruction at a non-symmetric plane was sufficient for the computation of the seven elastic constants. © 2006 Elsevier Ltd. All rights reserved.