In-vitro evidence of sorption of nitroglycerin (NTG) to polyvinylchloride (PVC) containers suggests that these containers may deliver less nitroglycerin to the patient than glass containers. Sorption of NTG to the PVC container may result in hemodynamic changes in the patient when a fresh solution of NTG is prepared and administered from a PVC container. This study was designed as a prospective, randomized trial to measure the hemodynamic response in patients receiving NTG in glass or PVC containers, during the first hour after a container exchange. Patients admitted to the coronary care unit in a University hospital with chest pain considered to be due to unstable angina or acute myocardial infarction were eligible. Patients who received other vasoactive drugs within one hour of container exchanges were excluded. Systolic and diastolic blood pressures, and heart rate were measured at baseline and at intervals for one hour following a container exchange. Twenty patients completed the study. There were no significant changes with time in either group (ANOVA, p > 0.05) with respect to systolic, diastolic, or mean arterial blood pressure or heart rate. No chest pain occurred during the 60 minutes following the container exchange in either group. We conclude that NTG can be administered safely and effectively in PVC containers to patients with unstable angina or acute myocardial infarction. However, it remains possible that changes in hemodynamic status could occur in patients on NTG if a change in container type (i.e., from PVC to glass or vice versa) is made during the course of therapy.