Objective— To evaluate the relationship between the type and duration of diabetes and pancreas size by ultrasonography. Research Design and Methods— Pancreas images of 40 IDDM and 36 NIDDM patients with 0.3–34 yr of disease were compared with those of 60 normal healthy control subjects. Results— The diameters ± SD of the head, body, and tail of the pancreas in IDDM patients (1.9 ± 0.3; 0.9 ± 0.2; and 1.4 ± 0.2 cm, respectively) were smaller than in NIDDM patients (2.7 ± 0.4; 1.2 ± 0.3; and 1.8 ± 0.4 cm, respectively) and control group subjects (2.4 ± 0.4; 1.1 ± 0.3; and 1.8 ± 0.4 cm, respectively). The pancreatic shrinkage in IDDM patients was clearly evident after 10 yr of the disease. NIDDM patients and control subjects had similar pancreatic dimensions, except for a greater body thickness in NIDDM patients with >10 yr of disease (1.2 ± 0.4 vs. 1.1 ± 0.3 cm). These results were not related to differences in age, sex, and body size. Pancreas image was hypoechogenic in 72.5% of IDDM patients and hyperechogenic in 83.3% of NIDDM patients. Conclusions— Smaller pancreases in IDDM patients in comparison with NIDDM patients and control subjects were clearly demonstrated only after 10 yr of disease. Patients with NIDDM were not affected by pancreatic dimensions, except for a greater body thickness after 10 yr of disease. Pancreatic echogenicity increased with age.