['EUS is the preferred modality for local staging of esophageal cancer. The presence of a long-lasting fluoroscopically visible marker of malignant lymph nodes would facilitate subsequent radiation and surgical therapy.', 'To assess the feasibility of EUS-guided implantation of a radiopaque marker (tantalum) into mediastinal and celiac lymph nodes in a porcine model.', 'Survival experiments on six 50-kg pigs.', 'A linear-array echoendoscope was advanced into the esophagus and the stomach. Mediastinal and celiac lymph nodes were identified and injected with 1 mL tantalum suspension by using 19- and 22-gauge FNA needles under fluoroscopy. The pigs were recovered. Fluoroscopy was repeated after 1, 2, and 4 weeks, then a postmortem examination was performed.', 'Long-term opacification of lymph nodes.', 'It was not possible to inject tantalum through the 22-gauge FNA needle because of its rapid precipitation inside the needle, which caused needle occlusion. Intranodal injection with the 19-gauge FNA needle was easily accomplished and resulted in excellent fluoroscopic opacification of injected lymph nodes. Repeat fluoroscopy at 1, 2, and 4 weeks demonstrated stable tantalum deposition at the injection site. There were no complications. Histologic examination of harvested lymph nodes revealed intranodal tantalum depositions without signs of infection, inflammation, tissue damage, or necrosis.'] Is eUS-guided implantation of radiopaque marker into mediastinal and celiac lymph nodes safe and effective?