Current data conflicts on ART outcomes in pts with 1O. Furthermore, data is limited evaluating embryo quality in these pts. We assessed number of mature oocytes (M2s) and total oocytes retrieved, embryo quality, and embryo transfer outcomes in pts with 1O compared to 2O. We performed a retrospective cohort study of all pts with 1O who underwent ART at one academic institution from 2012-2020. Pts were 3-to-1 matched to 2O controls by age, ART cycle type (oocyte freezing vs. embryo banking/in vitro fertilization) and number of ART cycles. Our primary outcome was number of M2s. Secondary outcomes included AMH and day 2 FSH prior to first cycle, number of retrieved oocytes, %M2s, 2PN fertilization rate, blastocyst formation rate (BFR), number of euploid embryos, euploidy rate, clinical pregnancy rate per pt (CPR), and live birth rate per pt (LBR). Subgroup analyses were performed comparing left vs. right ovary in situ and reason for loss of 1O. Mann-Whitney, Kruskal-Wallis, Fisher’s exact, and Wilcoxon signed-rank tests were used for statistics; with p<0.05 considered significant. 104 pts (158 cycles) with 1O were matched to 312 pts (474 cycles) with 2O. Reasons for loss of 1O were torsion (18%), benign cyst (30%), malignant tumor (46%), and congenital absence (6%). Median pt age was 35.5y vs. 35.0y in pts with 1O vs. 2O (p=0.9). AMH was lower (median 1.1 vs 2.2, p<0.01) and day 2 FSH was higher (median 7.4 vs 6.2, p<0.01) in pts with 1O. See Table 1 for outcomes. Pts with 1O had fewer M2s and oocytes retrieved than pts with 2O; however, pts with 1O had more than half the number of M2s and oocytes retrieved than in pts with 2O (Z >5.8, p<0.01). The % M2s, 2PN fertilization rate, and BFR did not differ among groups. The median number of euploid embryos was 1.0 in each group, with a trend towards more euploids in pts with 2O (mean 2.0 vs 1.3, p<0.03). However, euploidy rate, CPR, and LBR did not differ among groups. Among 1O subgroups (left vs. right and reason for 1O), number of M2s, euploidy rate, CPR, and LBR did not differ. Pts with 1O had fewer M2s and oocytes retrieved than pts with 2O; however, had more than 50% of the number of M2s and oocytes retrieved in pts with 2O, suggesting a compensatory mechanism in the solitary ovary. In pts with 1O compared to 2O, oocyte and embryo quality, euploidy rate, and embryo transfer outcomes were similar.