Renal fine-needle aspiration biopsy (FNAB) is used in several clinical scenarios: in patients with classic radiographic lesions; in non-operable patients with presumed high stage disease; and in patients with radiographic problematic lesions. Although overall, FNAB is a sensitive test, its role in the latter two populations has not been clearly established. To investigate the utility of FNAB in these patients, we retrospectively evaluated 43 renal FNABs in regards to diagnostic accuracy and clinical outcome. FNAB diagnoses were: malignant (36), suspicious (6), and insufficient (1). Our results indicate: 1) renal FNAB is accurate in patients with high stage lesions; 2) FNAB is less accurate in patients with radiographic problematic lesions; 3) the FNAB diagnosis of malignant increases the post-FNAB probability of malignancy, whereas the diagnosis of suspicious decreases the probability; and 4) there is excellent correlation for nuclear grade. We conclude that renal FNAB is useful in evaluating renal masses.