A step towards patient-individual RF ablation planning is the investigation of the inverse problem of tissue parameter identification. Currently, we focus on the identification of the electrical and thermal conductivity of the tissue. The conductivities are reconstructed from measurement data of the temperature distribution. By fitting the computed temperature to the measured data we formulate the inverse problem as an optimal control problem. Hence, we solve a minimization problem with the heat equation and the potential equation as constraints. To solve the minimization problem a sequential quadratic programming (SQP) method is used.