Routine monitoring of clinicopathologic data is a critical component in the management of older patients because blood and urine testing allows the veterinarian to monitor trends in laboratory parameters, which may be the early indicators of disease. Laboratory profiling often provides an objective and sensitive indicator of developing disease before obvious clinical signs or physical examination abnormalities are observed. The primary key to the power of this evaluation is that the data are collected year after year during wellness checks and are examined serially. Chronic renal failure, chronic active hepatitis, canine hyperadrenocorticism, diabetes mellitus, and feline hyperthyroidism were reviewed and expected laboratory findings are summarized.