The purpose of this study is to investigate the role that domain knowledge plays in users' interactions with information systems. Two groups of users with two different areas of expertise were recruited for 34 experimental sessions to answer two research questions: (a) Does one group's domain knowledge (Geography majors) affect their performance on an information system more than another group's domain knowledge (Computer Science majors)? (b) Are there any differences and/or similarities in the performance of the two groups in terms of the information problem-solving processes? Task completion time, task completeness, and mouse movements were collected while users performed six tasks during the experimental sessions. Data were analyzed through repeated measures. An ANOVA was used for task completion time and task completeness. GOMS (Goals, Operators, Methods, and Selection rules) was also used for mouse movements to identify some of the similarities and differences between the two groups' information problem-solving processes. The GOMS analysis found the two groups' processing activities to be remarkably similar. The ANOVA results indicate that expertise type was not a major factor influencing user performance, but task and task combined with the type of expertise played a significant role in the users' interactions with the interface. External operators, goal decompositions, and methods related to the problem solving process through GOMS are also presented.