To find out whether ultrasound-guided fine-needle aspiration (FNA) and ultrasound and stereotactic-guided large core needle biopsy (LCNB) are reliable alternatives to needle-localised open breast biopsy (NLBB) in daily practice, we performed a retrospective study and evaluated the validity of these methods. In all, 718 women with 749 nonpalpable breast lesions from three Dutch Hospitals were included, and the validity of the various methods for diagnosis was assessed. This was carried out according to a method described by Burbank and Parker for evaluating the quality of an image-guided breast intervention. We compared our results with the outcome of the COBRA study. Overall, all diagnostic strategies (NLBB, FNA, LCNB ultrasound and stereotactic guided) show comparable agreement rates. However, the miss rates differ: 2% for NLBB, 3% for COBRA (LCNB in study setting), 5% for FNA and 8 -12% for LCNB in practice. Fine-needle aspiration was nonconclusive in 29%, and shows an overestimation for DCIS in 9%. The DCIS underestimate rate in NLBB was 8%. For the assessment of lesions consisting of microcalcifications only and to exclude malignancy in all other lesions, a 14-gauge needle should be used. Ultrasound-guided intervention can be performed in a large percentage of nonpalpable lesions. Lesions consisting only of microcalcifications on mammography need special attention. Needle-localised open breast biopsy (NLBB) is considered the gold standard procedure for the diagnosis of nonpalpable breast lesions (NPBL) (Jackman and Marzoni, 1997). Needle-localised open breast biopsy is a surgical procedure with high costs and for most of the patients, is a traumatic experience. In the past few decades, less traumatic and cost-saving nonoperative image-guided techniques, such as fine-needle aspiration (FNA) and large-core needle biopsy (LCNB), have been advocated as an alternative to surgery to obtain material for a microscopic diagnosis. For guidance, ultrasound or stereotaxis are advocated.Recently, a large prospective study on stereotactic-guided LCNB was performed in the Netherlands to evaluate the diagnostic accuracy of this method (COBRA study) (Verkooijen, 2002). This study included 973 patients with 1029 nonpalpable breast lesions and showed a sensitivity rate of 97% and a specificity rate of 99% for stereotactic-guided LCNB. These figures are comparable to NLBB (Jackman and Marzoni, 1997). In the Dutch study, the stereotactic LCNB was always performed on a dedicated prone table, in an optimal setting. The dedicated equipment appears to be highly reliable but has the disadvantage of high initial expense. Therefore, it is not widely available in the Netherlands. The other alternatives for NLBB, such as stereotactic-guided LCNB with upright mammography machine and add on digital attachment, ultrasound-guided FNA and LCNB are more widely available. To find out whether FNA (ultrasound-guided) and LCNB (ultrasound and stereotactic-guided) are reliable alternatives to NLBB in daily practice, a retrospective study on the dia...