This article describes a procedure for obtaining the partial derivatives of experimental data that depend on two independent variables. The starting equation is an ill-posed integral equation of the first kind. Tikhonov regularization is used to keep noise amplification under control. Implementation of the computation steps is described and the performance of the procedure is demonstrated by four practical examples. (C) 2010 American Institute of Chemical Engineers AIChE J, 56: 3212-3224, 2010