Online prescription filling possesses great market potential; however, consumers' perception of uncertainty tends to impede their adoption of online prescription filling. Trust is recognized as a critical factor affecting online shopping in general. We contend that trust can help consumers overcome perceived uncertainty, thereby enhancing their intention to adopt online prescription filling. Drawing on prior research on trust and theory of transaction cost economics, this paper proposes a research model that encompasses three trust antecedents, two sources of uncertainty, and the relationships among trust, uncertainty, and the consumer's intention to adopt online prescription filling. The model was tested empirically using a large sample. It was found that (1) calculus-based, knowledge-based, and institution-based trust antecedents significantly affect trust, (2) information asymmetry and online drug retailers' opportunistic behavior contribute to perceived uncertainty, (3) trust reduces uncertainty and positively affects intention, and (4)uncertainty influences intention negatively.