Abstract Three related studies replicated and extended previous work (J.A. Danielson et al. (2003), Educational Technology Research and Development, 51(3), 63–81) involving the Diagnostic Pathfinder (dP) (previously Problem List Generator [PLG]), a cognitive tool for learning diagnostic problem solving. In studies 1 and 2, groups of 126 and 113 veterinary students, respectively, used the dP to complete case-based homework; groups of 120 and 199, respectively, used an alternative method. Students in the dP groups scored significantly higher (p = .000 and .003, respectively) on final exams than those in control groups. In the third study, 552 veterinary students responding to a questionnaire indicated that the dP’s gating and data synthesis activities aided learning. The dP’s feedback and requirement of completeness appear to aid learning most. Keywords Cognitive Load Theory Æ Cognitive Tools Æ Diagnostic Problem Solving Æ Feedback Æ Gating J. A. Danielson (&) Æ E. M. Mills Æ P. J. Vermeer Æ V. A. Preast Æ H. S. Bender Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA e-mail: jadaniel@iastate.edu K. M. Young Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, 2015 Linden Drive, Madison, WI 53706-1102, USA M. M. Christopher Æ J. W. George Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, 1153 Haring Hall/128 Surge IV, Davis, CA 95616, USA R. Darren Wood Department of Pathobiology, University of Guelph, Guelph, ON N1G 2W1, Canada 123 Education Tech Research Dev (2007) 55:499–520 DOI 10.1007/s11423-006-9003-8 DEVELOPMENT ARTICLE Characteristics of a cognitive tool that helps students learn diagnostic problem solving Jared A. Danielson Æ Eric M. Mills Æ Pamela J. Vermeer Æ Vanessa A. Preast Æ Karen M. Young Æ Mary M. Christopher Æ Jeanne W. George Æ R. Darren Wood Æ Holly S. Bender Published online: 20 September 2006 Ó Asssociation for Educational Communications and Technology 2006