Diagnosis and management of giant cell (temporal) arteritis (GCA) should be performed by physicians who can accurately monitor the ophthalmologic, neurologic, and systemic sequelae of the disease as well as the numerous side effects of systemic corticosteroids, which are typically necessary for treatment. When the diagnosis of giant cell arteritis is seriously entertained, early treatment with adequate doses of oral or intravenous corticosteroids should not be delayed until laboratory confirmation has been obtained. Unilateral or bilateral temporal artery biopsy should be performed on all patients with suspected GCA. A positive biopsy result mandates that higher doses of corticosteroids be used during the first 2 months, which comprise the critical period for risk of new ocular ischemia. A definitive, biopsy-proven diagnosis requires at least 6 months, and typically 12 months, of corticosteroid therapy. Common pitfalls include increasing the dose and prolonging the use of corticosteroids in response to increases in the erythrocyte sedimentation rate (ESR) unrelated to GCA or visual blurring that may be related to benign tear film abnormalities, corticosteroid-induced lens changes, and other ophthalmic conditions. The muscle stiffness of polymyalgia rheumatica (PMR) must be distinguished from the osteoarthritis and other painful conditions common in the elderly. After corticosteroid therapy has begun, continuing ophthalmologic evaluation is necessary to evaluate the effectiveness of treatment and whether ocular complications, such as glaucoma or cataract, develop. Careful attention must be given to early detection and prevention of systemic side effects of corticosteroid treatment. Patients may be given gastrointestinal protective agents, such as histamine (H(2))-blocking agents; vitamin D and calcium; oral hypoglycemic agents; and, if necessary, insulin and antihypertensive drugs. If bone density measurements warrant, hormones/supplementation to prevent or reverse osteoporosis may be prescribed. After the initial diagnosis and first 4 weeks of treatment, elevation of the ESR or C-reactive protein alone should generally not be used as signs of disease activity nor as a reason to increase the daily dose of steroids. If symptoms or signs of disease activity occur, the dose should be raised regardless of test results. Even with vigorous physician-patient education, however, a patient is occasionally unable to provide adequate historical information about response to therapy, and the physician is forced to rely on laboratory values as a measure of disease activity. After initial high-dose corticosteroid therapy, patients without a classic history and with negative biopsy results will generally receive a rapid taper to low doses of corticosteroids. The role of repeated temporal artery biopsy in the clinical management of GCA is unclear. Despite persistence of PMR and, in some cases, histologic evidence of inflammation in temporal arteries, patients do not frequently have recurrence of symptomatic GCA after 6 months or more of corticosteroid therapy. Under these circumstances, late vision loss is rare.