Abstract. Objectives: To compare a composite of severe adverse outcomes of care using the open-bay (OPBY) and single-family room (SFR) neonatal intensive care unit (NICU) designs. Study design: Retrospective cohort analysis of a composite indicator of death, grade III-IV intraventricular hemorrhage, >28 days of supplemental oxygen or the need for retinal laser ablation surgery. Data for 3143 neonates over a ﬁve-year period were analyzed. Propensity score was calculated as the predicted probability of a neonate being admitted to the OPBY NICU. This indicated that the two cohorts were comprised of similar subjects. Equivalence testing was also used to compare the two study cohorts with logistic regression modeling the occurrence of the composite endpoint. Results: Logistic regression did not indicate a signiﬁcant difference in composite adverse outcomes for the OPBY and SFR NICU. Equivalence testing and the use of the propensity scores conﬁrmed the comparability of the two study cohorts. Conclusions: The large sample and the conﬁrmation of equivalence of the two study cohorts provides great conﬁdence that in this investigation there was no difference in composite of serious adverse outcomes of care using either the OPBY or SFR NICU design.