OBJECTIVE: The purpose of this study was to determine the stability of oxytocin in lactated Ringer's solution and lactated Ringer's–dextrose 5% solution over a 24-hour period at 25°C and over a 7-day period at 5°C. STUDY DESIGN: Twenty units (2.1 μg equal 1 unit) of oxytocin were injected into 1000 mL of lactated Ringer's solution and lactated Ringer's–dextrose 5% solution. Samples for the analysis were drawn at specified times after storage at 5°C and 25°C. These samples were stored at −70°C for later analysis. Statistical analysis was done with 1-way analysis of variance and Tukey-Kramer multiple comparisons. RESULTS: Twenty units of oxytocin in 1000 mL of lactated Ringer's solution and lactated Ringer's–dextrose 5% solution was found to be stable for 7 days at 5°C and for 24 hours at 25°C. CONCLUSION: Premixed oxytocin solutions in lactated Ringer's solution and lactated Ringer's–dextrose 5% solution are stable in conditions commonly found in dispensing pharmacies and labor and delivery units. This finding could lead to the more efficient use of personnel during the mixing process, could provide solutions that are aseptically prepared, and could be a tool to reduce costs and improve patient care. (Am J Obstet Gynecol 2002;186:496-8.)