Objective: The objective of the study was to establish the compatibility of injectable meropenem with 101 other drugs during Y-site administration. Methods: Meropenem (50 mg/mL, 10 mL) was combined with 101 undiluted injectable drugs (10 mL each) at room temperature. Each preparation was performed twice. The first sample underwent a visual evaluation and a particle count test by light obstruction immediately after mixing. These tests were repeated 4 hours after mixing using the second preparation. Incompatibility was defined as precipitation or other visual change (turbidity, crystal formation, gas formation, color change) or failure to meet United States Pharmacopeia (USP) <788> 1.B specifications at any time point. Results: A total of 83 of the 101 injectable drugs tested with meropenem were found to be compatible both visually and using the USP <788> particle counter. The gross incompatibility of the other 17 drugs was determined by visual observation. One mixture complied with the specifications, but showed an increase of temperature upon mixing and was removed from the study. Conclusion: Of the 101 drugs tested, 83 were found to be compatible while the remaining 17 were incompatible. One drug was removed from the study as its compatibility was unclear.