Background and study aims: The prevalence of periduodenal venous collaterals detected by endoscopic ultrasonography (EUS) in patients undergoing evaluation for pancreaticobiliary disorders, and their influence on the success of transduodenal fine-needle aspiration (FNA) of solid pancreatic masses is not known. Patients and methods: Records for all consecutive patients who underwent EUS for pancreaticobiliary disorders over a 14-month period were reviewed. EUS was carried out by a single endosonographer using a radial echo endoscope. When FNA was attempted, a curvilinear-array echo endoscope was used in conjunction with color flow Doppler. Periduodenal and perigastric collaterals were defined as multiple anechoic serpiginous structures imaged from the duodenal bulb, the second portion of duodenum, or the stomach. Established criteria were used to assess the presence of chronic pancreatitis. Results: Over the study period, 338 patients (mean age 58.9 ± 14.5 years; 52% women) underwent EUS for pancreaticobiliary disorders. Periduodenal collaterals were detected in 22 patients (6.5%), 21 of whom (19%) had pancreatic cancer. Patients with pancreatic cancer were significantly more likely to have periduodenal collaterals in comparison with those without pancreatic cancer (OR 25; 95%CI, 5.75-109; P = 0.001). Computed tomography detected collaterals in only two of the 22 patients (9.1 %). Periduodenal collaterals made transduodenal FNA impossible in nine of the 22 patients (41 %). However, in these patients a cancer diagnosis was obtained using EUS-FNA from liver lesions in two cases; using a transgastric approach in two (pancreatic neck lesions); and atypical cells were obtained in two. A safe window could not be achieved in three patients (13.6%). Transduodenal FNA was performed by avoiding the collaterals and was successful in 13 of the 22 patients, with no bleeding complications. Conclusions: Periduodenal collateral vessels are infrequent in patients with suspected pancreaticobiliary disease, but are relatively common in patients with pancreatic cancer. Transduodenal EUS-FNA can be carried out safely in the majority of cases in the presence of periduodenal collaterals, but collaterals may occasionally hamper successful transduodenal pancreatic FNA.