This work, involved with the load modeling for electrical system transiente stability analysis, aim to discuss the classical load models normally used, and to develop and improve representations of specific types of loads. Initially, aspects concerned with classical load representations are dealt with aiming to evaluate, through theoretical and computational analyses, the current employment of such models. Knowing that the techiques to obtain induction motor parameters are still deficient, this work presents some systematic procedures for the treatment of such loads. Additionally, it continues seeking improvements in electrical system component models and answers to the questions about the need for inclusion of the frequency variation effects on loads and network parameters. Moreover, it takes into account the tendencies of using simplified load models represented by algebraic expressions. Some recent proposals in this area are discussed and tested with a view to acess the perfomance of the models in stability studies. Finally, considering the present importance of static load converters, it is developed the related models and presented the necessary studies to include rectifier units in stability programs.