Background/Aims: Endosonography is associated with a long learning curve. We aimed to assess variables that may influence the diagnostic outcomes in endoscopic ultrasound-guided fine-needle aspiration/biopsy (EUS-FNA/B) of solid pancreatic tumors regarding the level of endoscopists' experience. Methods: Consecutive patients undergoing EUS-guided puncture of solid pancreatic tumors (eight endosonographers, including six trainees) were prospectively enrolled. An experienced endosonographer was defined as having performed at least 250 EUS examinations, including 75 FNA/Bs. The final diagnosis was determined by cytopathology, histopathology, or clinical followup. Results: In total, 283 EUS-FNA/Bs of solid pancreatic tumors (75.6% malignant) in 239 patients (median age 69 years, 57.6% males) were enrolled. Trainees performed 149/283 (52.7%) of the interventions. Accuracy and sensitivity for detecting malignancy were significantly higher in the expert group than in the trainee group (85.8% vs 73.2%, p=0.01 and 82.5% vs 68.4%, p=0.02). Solid lesions evaluated by an expert using FNB needles showed the best odds for a correct diagnosis (odds ratio, 3.07; 95% confidence interval, 1.15 to 8.23; p=0.02). More experienced endoscopists achieved better accuracy in sampling via the transduodenal approach (86.7% vs 68.5%, p<0.001), in the sampling of malignant lesions (82.5 vs 68.4, p=0.02), and in the sampling of lesions located in the pancreatic head (86.1 vs 69.1, p=0.02). In cases involving these factors, we observed a moderate improvement in the diagnostic accuracy after 40 attempts. Conclusions Transduodenal approach, pancreatic head lesions, and malignancy were recognized as the most important clinical factors affecting the learning curve in EUS-FNA/B of solid pancreatic lesions.