In this work we describe, apply and analyze a procedure to extract the physical parameters of a solar cell from its I-V curve under illumination. We compare it with other procedures and assess the statistical significance of the parameters. Our method, called APTIV, uses separate fitting in two different zones in the I-V curve. In the first one, near short circuit, current fitting is used because the error in current dominates. In the second one, near open circuit, voltage fitting is used because this is the dominant error. The method overcomes some drawbacks of common procedures: voltage errors are properly managed and no accurate initial guesses for the parameters are needed. In addition, the numerical implementation is very simple. (c) 2004 Elsevier B.V. All rights reserved.