This article outlines strategies on how to approach equine endocrine disorders based on clinical signs and clinical pathologic data. In the 1987 Veterinary Clinics of North America: Equine Practice article on evaluating equine endocrine function, Beech stated that the numbers of hormonal assays available to use in horses was limited. Unfortunately, not much has changed since then. With the advent of convenient assay kits for many hormones and cofactors available in human medicine, it is possible to submit samples to laboratories for measurement of a wide range of endogenous substances. Caution must be used when interpreting the results in equine patients. Assay kits that have not been validated for use in horses may yield results that have no clinical meaning. Using veterinary endocrinology laboratories with equine experience is the best way to assure meaningful results from diagnostic testing (Table 1). If this is not possible, submitting age, breed, and sex-matched controls along with samples from the patient horse will provide some measure of a reference range. Normal values or reference ranges from species other than the horse cannot be used to interpret the results of equine samples.