Sclerotherapy is a surgical procedure used for vascular and lymphatic malformations, in all age groups, wherein a sclerosing agent is injected into a vessel to make it shrink. It involves injection of the agent intravascularly intralesionally or topically, under direct vision or under the guidance of radiological imaging. Sclerotherapy has primarily been used in ophthalmology for treatment of arteriovenous malformations like hemangiomas and carotico-cavernous fistulas, and lymphatic abnormalities like lymphangiomas. Sclerosing agents are chemical compounds which cause endothelial injury leading to inflammation and vascular thrombosis. They may be classified into various categories like detergents, hyperosmotic agents, corticosteroids, cytotoxic agents etc. A short description on beta-blockers has also been included in this article, even though beta-blockers are not sclerosants per se. Polyvinyl alcohol, sodium tetradecyl sulphate (STS) and ethanol may be used for arterio-venous malformations, while for lymphangiomas agents like sodium morrhuate, STS, doxycycline and OK-432 are used. In hemangioma patients, corticosteroids and beta-blockers are amongst the first line therapy.