This article addresses the development of relationship quality in the service context of information technology (IT) based on the network externalities theory. The model predicates the IT relationship quality is influenced by both synchronization value and autarky value, whereby autarky value is influenced by the availability of complementary goods. At the same time, synchronization value is influenced by relationship commitment and perceived critical mass, while availability of complementary goods is influenced by perceived compatibility and overall installed base. Note that the autarky value represents the value generated by the product itself even if there are no other users (e.g., the printing and copying functions of a fax/printer machine), while synchronization value represents individuals' perceived value obtained through interaction (e.g., chatting functions of Skype). The model is examined using data obtained from employees of different companies in Taiwan. The empirical findings and their implications are discussed herein.