There is a constantly increasing need for dynamically trading intangible goods in today's economies. Electronic markets for intangible goods are on the rise. IT-based services support transaction activities between suppliers and customers. The vital task is negotiating a contract. Managing flexible transactions with varying market partners, considering multidimensional terms and conditions, and acting within short periods of time are crucial challenges for automated negotiation services of electronic markets. The approach of intelligent software agents as a negotiation service is presented. Aspects on negotiation protocol, software agent design and implementation are outlined. Insights into sample experiments and results are given.