Thirty-seven cases of canine hypoadrenocorticism were compared with 39 previously reported cases. The 2 series were compared because it was believed that a study of 37 consecutive cases diagnosed at 1 institution (Michigan State University) and compiled by 1 group of veterinarians would yield data that were more representative of the disease than multiple cases from various institutions. Age, sex, and breed data were similar in both series. The frequency of anorexia, vomiting, depression, and the mean values for the clinicopathologic data were similar for both series except for blood glucose concentration (P less than 0.025). The Michigan State University series was different in that it had a lower frequency of eunatremia, increased plasma total solids, and hypoglycemia but a higher frequency of lymphocytosis, lymphopenia, hyponatremia, hyperglycemia, and hypercalcemia. Further, 3 dogs in the Michigan State University series had azotemia plus near isosthenuric urine, suggesting renal disease, but they seemingly responded to therapy for hypoadrenocorticism. Only 1 such case was identified in the literature. Finally, we detected fewer instances of P waves not being evident in lead II of an electrocardiogram.