Background: A new mechanical sector scanning echoendoscope designed for EUS-guided, fine-needle aspiration biopsy (FNAB) was prospectively evaluated. The technical feasibility, safety, and histocytologic FNAB results are reported. Methods: Eighty-six patients underwent 106 FNAB procedures. The new echoendoscope has a 2.8 mm accessory channel and an elevator. Target sites: pancreas 58, lymph nodes 43, and miscellaneous lesions 5. Lesions were punctured with a 0.7 mm needle and submitted for cytologic and histologic examination. Definitive diagnosis was by surgery or clinical follow-up. Results: The wide scanning field (250 degrees) enabled easy sonographic orientation for FNAB. Longitudinal needle visibility was “good” in 93% and 71% of transesophageal and transgastric procedures, respectively, but were compromised during most transduodenal procedures. Needle penetration of indurated pancreatic lesions failed in two patients, and in four additional patients pancreatic sampling succeeded only after a second attempt using an automated spring-loaded device. The mean number of passes was three. Ten percent of FNAB specimens were “inadequate”; excluding these, the diagnostic accuracy rate was 97%; sensitivity for malignancy was 88.5% and specificity was 100%. Conclusion: EUS-guided FNAB is feasible, safe, and accurate using the new mechanical puncture echoendoscope. Needle visibility needs to be improved, particularly for transduodenal FNAB. (Gastrointest Endosc 1998;47:335-40.)