This paper describes the use of a genetic algorithm to fit multi-Debye functions to the dielectric properties of body tissue. The most accurate models of body tissue at present are multi Cole-Cole functions. The Cole-Cole functions include an additional parameter which improves the agreement of the model with real measured tissue data, but this additional parameter makes the input of these functions within computer simulations difficult. The Debye functions can be input into computer simulations easily. In this work an equally good model as the Cole-Cole model is achieved simply by using additional Debye functions within the multi-Debye model of the tissue data. This enables body tissue data to be easily implemented within time domain models.