The adrenal glands of twenty-six, 12- to 53-month-old, ferrets without clinical signs of adrenal disease were examined and measured by ultrasonography and the findings compared with those from gross examination and histopathology. Of 51 adrenal glands examined, 27 were normal, 23 had either nodular or diffuse cortical hyperplasia and 1 had an adenocarcinoma. There was no statistically significant difference between the sonographic nor gross size of normal adrenal glands and those with hyperplasia. Moderate correlation was found between gross and sonographic measurements of length for both right (r = 0.783; p < 0.0001) and left (r = 0.609; p < 0.001) and width (p < 0.02). In female ferrets, the length, width, and depth of the right adrenal gland sonographically measured (mean +/- sd) 7.5 +/- 1.2 mm, 3.7 +/- 0.6 mm, 2.8 +/- 0.4 mm, respectively, and the left measured 7.4 +/- 1.0 mm, 3.7 +/- 0.4 mm, 2.8 +/- 0.4 mm; in males, the right adrenal measured 8.9 +/- 1.6 mm, 3.8 +/- 0.6 mm, 3.0 +/- 0.8 mm and the left measured 8.6 +/- 1.2 mm, 4.2 +/- 0.6 mm, 3.0 +/- 0.6 mm. Accessory adrenal tissue was not identified during the sonographic examination but was grossly found in 10 of the ferrets. It was associated with either the right, left or both adrenal glands.