Introduction: The administration of medications to patients is practices by undergraduate nursing students in health care facilities during their clinical placements. It is a skill that demands students to perform safely and accurately whilst also being supervised appropriately. This paper reports on a study which examined the experiences of undergraduate nursing students when administering medications in the clinical setting. Method: A grounded theory approach with constant comparative analysis informed the development of an explanatory substantive theory. A sample of 28 final year undergraduate nursing students from a regional university provided data in order for theory development. Results: This study identified supervision as a central issue for students which ultimately influenced their decision making at the time of administering. Supervision levels were identified as ranging from the registered nurse being close and personal to being absent. Supervision shifted to levels which identified as causing internal conflict for students and ultimately influenced their practice. Medication errors were identified as more apparent when the supervision of students was less than adequate. More importantly errors were prevented when supervision was present at a personal and direct level. Discussion: This study has identified that the supervision of students when administering medications can be less than ideal. Different levels of supervision have been identified together with student behaviours in response to the supervision. This study has provided recommendations that rea now being acted upon in some Queensland health care facilities and universities. The recommendations, including strategies to teach medication safety for example; high fidelity patient latex simulation, may serve as useful for other organisations which involve students administering medications.