['To assess the biological effects of passage through clinically relevant needles on the viability and metabolic activity of culture-expanded, human adipose tissue-derived mesenchymal stromal/stem cells (AMSCs).', 'Prospective observational pilot study.', 'Academic medical center.', 'Patient-derived clinical-grade culture expanded AMSCs.', 'AMSCs were passed through syringes without a needle attached (control), with an 18-gauge (25.4-mm) needle attached and with a 30-gauge (19-mm) needle attached at a constant injection flow rate and constant cell concentrations. Each injection condition was completed in triplicate.', 'Cell number and viability, proliferative capacity, metabolic activity, and acute gene expression as measured by cell counts, mitochondrial activity, and quantitative real time reverse-transcription polymerase chain reaction on day 0 (immediately), day 1, and day 4 after injection.', 'AMSC viability was not significantly affected by injection, and cells proliferated normally regardless of study group. Postinjection, AMSCs robustly expressed both proliferation markers and extracellular matrix proteins. Stress-response mRNAs were markedly but transiently increased independently of needle size within the first day in culture postinjection.'] Do human Adipose-Derived Mesenchymal Stromal/Stem Cells Remain Viable and Metabolically Active Following Needle Passage?