Neurologic diseases tend to have a species, age, breed, and occasionally a sex predilection. The primary complaints for neurologic problems often include behavioral changes, seizures, tremors, cranial nerve deficits, ataxia, and paresis or paralysis of one or more limbs. Information about the onset, course, and duration of the primary complaint can be used to determine the most probable disease mechanisms. Congenital and familial disorders are most common in purebred animals at birth or within the first few years of life. Inflammatory, infectious, metabolic, toxic, and nutritional disorders can be seen in any species, breed, or age; tend to have an acute or subacute onset; and are usually progressive. Vascular and traumatic disorders have an acute onset and rarely progress after 24 hr. Most degenerative and neoplastic disorders tend to be seen in older animals (except for familial neuronal degeneration) and have a chronic onset and progressive course. Many idiopathic disorders begin acutely and improve throughout a short time. Information about similar familial problems, concurrent or recent systemic disease, vaccination status, other affected animals, diet, possible exposure to toxins or trauma, and past neoplastic disorders may be useful to further support certain mechanisms of disease.