Fine-needle aspiration (FNA) cytology for the diagnosis of malignant lesions has been used in gynecologic oncology for a long time. Core biopsies have also been used for the same purpose for many years but there are, to my knowledge, no reports in the literature of the use of core biopsies in the diagnosis of gynecologic lesions. The purpose of this study was to evaluate the accuracy of these two methods in gynecologic cancer. This study comprises 85 patients examined from 1986 through 1995. The histology and cytology of gynecologic lesions were investigated by the use of an automatic biopsy instrument (Biopty) with a specially designed needle guide. Concomitantly all patients underwent FNA for cytology. Three hundred thirty-nine FNA and 141 biopsies using the Biopty core instrument (BCI) were obtained from patients with persistent, recurrent, or metastatic disease. Correct diagnosis was made with FNA cytology in 67/85 (79%) and with BCI in 62/85 (73%) of the cases (P = 0.08). Insufficient material for evaluation was recorded for FNA in 12/85 (14%) compared to 10/85 (12%) for the BCI (P = 0.29). False-negative diagnoses occurred in 5% of the cases with FNA compared to 15% with BCI (NS). The sensitivity of FNA was 92% and that of BCI 73% (P = 0.01) and the specificities 92 and 100% (NS), respectively. The predictive values of positive results for the two methods were 96 and 100%, respectively. The complication rate was negligible. In conclusion, FNA in combination with BCI in gynecologic lesions is a simple and safe operation using needle guides. In comparison with FNA cytology the sensitivity for BCI is lower but the specificity is higher. No significant differences were found in accuracy between the two methods. BCI biopsy should be considered in the subset of patients where additional information about the tumor is desired for planning the treatment of recurrent disease.