Objectives: Core needle biopsy (CNB) and fine-needle aspiration (FNA) for tumors of suspected Müllerian origin may prevent unnecessary laparotomies and allow patients the benefit of neoadjuvant chemotherapy. An assessment of the utility and limitations of CNB/FNA, with incorporation of current immunohistochemistry, is needed. Study Design: Two hundred nineteen female patients with CNB/FNA of the omentum, pelvis, abdomen, adnexa, ovary, uterus, and fallopian tube were identified. From these, 30 consecutive CNB/FNA with corresponding surgical resection were reviewed to assess diagnostic agreement and identify potential diagnostic pitfalls. Results: The most frequent diagnosis overall was adenocarcinoma (96/219; 43.8%), most commonly adenocarcinoma of gynecologic origin (65/219; 30%). Nondiagnostic or unsatisfactory material was present in a minority of cases (10/219; 5%). In the 30 CNB/FNA cases examined for diagnostic agreement with surgical resection, 24 (80%) had exact or essential agreement with the final diagnosis. Of the 23 cases that were positive and/or suspicious on cytology, 18 (78%) had neoadjuvant chemotherapy or radiation treatment prior to surgical resection. Conclusions: The majority of CNB/FNA for tumors of suspected Müllerian origin are diagnostic, correlate with the surgical resection, and contribute to management. A standard diagnostic algorithm is suggested.