Mastocystosis is a rare disease for which treatment with cladribine (2-chlorodeoxyadenosine) was first reported in 2001. Cladribine has meanwhile been administered in over hundred reported cases and is available for intravenous and subcutaneous administration. Cladribine has mainly been used in systemic mastocytosis and in larger series responses were obtained in over 50% of cases in which treatment with H1/H2 blockers, interferon or tyrosine kinase inhibitors did not induce a response. Literature describing the use of cladribine in mastocytosis is reviewed herein.