Sodium antimony gluconate (SAG) and miltefosine used in the treatment of kala-azar are known to cause several side effects but severe thrombocytopenia has not been reported. Four cases of severe thrombocytopenia, two caused by SAG and two by miltefosine were promptly detected and treated by immediate withdrawal of the offending drugs, platelet and blood transfusions and dexamethasone. After improvement Leishman-Donovan (LD) bodies were demonstrated in splenic aspirates of both patients of SAG group and one of miltefosine and they were treated with 1 mg/kg body wt of amphotericin B for 20 days and cured. One patient of miltefosine group treated outside only on the basis of rK-39 positivity did not show LD bodies in splenic aspirates and improved without any antikala- azar drug. None of the patients relapsed within 6 months of follow up. Prompt detection of side effects under the concept of pharmacovigilance can save life of such patients.