Objectives. The purpose of this study was to describe changes in critical thinking ability and disposition over a 4-year Doctor of Pharmacy curriculum. Methods. Two standardized tests, the California Critical Thinking Skills Test (CCTST) and California Critical Thinking Dispositions Inventory (CCTDI) were used to follow the development of critical thinking ability and disposition during a 4-year professional pharmacy program. The tests were given to all pharmacy students admitted to the PharmD program at the College of Pharmacy of North Dakota State University (NDSU) on the first day of classes, beginning in 1997, and repeated late in the spring semester each year thereafter. Results. Increases in CCTST scores were noted as students progressed through each year of the curriculum, with a 14% total increase by graduation (P<0.001). That the increase was from a testing effect is unlikely because students who took a different version at graduation scored no differently than students who took the original version. There was no increase in CCTDI score. Conclusion. The generic critical thinking ability of pharmacy students at NDSU's College of Pharmacy appeared to increase over the course of the program, while their motivation to think critically did not appear to increase.