Faced with the ongoing evolution of software agents from mere passive tools to e-tailers acting autonomously for their human owners (principals), new legal challenges appear on the agenda. One of them is the question, whether the traditional law of agency that regulates the legal issues arising from human agents constituting legal relations between their principal and a third party, is applicable for software agents as well. Based on the characteristics of software agents this paper examines approaches for a legal classification of software agents and thereby analyzes current legislation that deal with the conclusion of contracts by software agents. Finally, this paper addresses remaining legal questions and discusses proposed solutions. Categories and Subject Descriptors K.5 [Legal Aspects of Computing]: Miscellaneous General Terms Legal Aspects Keywords Legal Aspects, Law of Agency, Software Agents