The purpose of this study was to examine how nursing efficacy for drug-dosage calculation instruction is determined. Medication administration is a critical function of nurses in healthcare settings. An essential component of safe medication administration is accurate drug-dosage calculation, but instruction in drug-dosage calculation methods provided by nursing faculty has not consistently resulted in students' mastery of the calculation skills necessary for successful medication administration. The faculty perspective of how teachers form their teaching behaviors and an exploration of their perceptions of teaching efficacy for this area of instruction is missing from the literature. A basic qualitative research design was used for this study. Sixteen nursing faculty members responsible for classroom drug-dosage calculation instruction were interviewed during 2010 about their experiences teaching this content. The participants were recruited from prelicensure baccalaureate nursing programs within one Midwestern state. The participants represented public, private, and for-profit nursing programs from urban, suburban, and rural areas of the state. Two themes emerged from this study: human attributes and experiences influenced teaching efficacy and system attributes influenced teaching efficacy. Data gathered about participants' personal and professional history with math and drug-dosage calculation as well as resources available to them in teaching drug-dosage calculation contributed to the picture of how teaching efficacy for this content was determined. Six conclusions were drawn from this study. Nursing faculty members' personal and professional history with math exerts a profound influence on their teaching efficacy, as do their values and beliefs about students, the profession, and the teaching-learning process. Graduate education in nursing did not prepare these new faculty members to teach, particularly drug-dosage calculation. External influences and teaching experience play a role in determining a faculty member's teaching efficacy for dosage calculation. Finally, the findings of this study support the teaching efficacy conceptual model as a tool in understanding how teaching efficacy is determined for nursing faculty teaching DDC. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]