Purpose: To describe inter- and intraobserver reliability of 3D measurements of female pelvic floor structures. Materials and Methods: Twenty reconstructed MR datasets of primiparas at 6-12 months postpartum were analyzed. Pelvic organ measurements were independently made twice by three radiologists blinded to dataset order. A "within-reader" analysis, a "between-reader" analysis, and the intraclass correlation (ICC), and standard deviation ratio (SDR) were computed for each parameter. Fifteen continuous variables and one categorical variable were measured. Results: Eight continuous parameters showed excellent agreement (ICC >0.85 / SDR <0.40), five parameters showed relatively good agreement (ICC >0.70 / SDR ≥0.40, <0.60). Two parameters showed poor agreement (ICC ≤0.70 and/or SDR ≥0.60). The categorical variable showed poor agreement. Conclusion: Agreement was best where landmark edges were well defined, acceptable where more "reader judgment" was needed, and poor where levator defects made landmarks difficult to identify. Automated measurement algorithms are under study and may improve agreement in the future. © 2009 Wiley-Liss, Inc.