Subacute lymphocytic thyroiditis (painless/silent thyroiditis) is characterized by an autoimmune-mediated lymphocytic inflammation of the thyroid gland resulting in a destructive thyroiditis with release of thyroid hormone and transient thyrotoxicosis (hyperthyroidism). This is frequently followed by a longer hypothyroid phase before recovery of normal thyroid function in most, but not all, patients. Silent lymphocytic thyroiditis affects mostly women in the post-partum period. It is classified into (1) sporadic type, which includes thyroiditis unrelated to pregnancy, (2) post-partum thyroiditis and gestational painless thyroiditis; (3) exogenous (drug-induced) painless thyroiditis; and (4) “others” including that induced by neck radiation, operative trauma, and post-131I therapy for Graves’ disease. The disorder often goes undiagnosed. Management of painless thyroiditis depends on patient presentation and disease phase. In general, treatment is not necessary for asymptomatic or mildly symptomatic patients. Because silent lymphocytic thyroiditis lasts only a few months, treatment is conservative. Anti-thyroid medications are not used as they are ineffective. Surgery and radioactive iodine (RAI) therapy are contraindicated. A beta-blocker is often needed in the hyperthyroid phase, and thyroid hormone replacement is typically needed in the hypothyroid phase. This disorder usually recurs after subsequent pregnancies. Recurrent disease is treated in the same manner as the initial occurrence, though patients with “multiple” recurrences may opt for surgery or RAI ablation of the thyroid (after recovering from the thyrotoxic phase).