This is a prospective, open-label, single center, pharmacokinetic study of anidulafungin in infants and toddlers less than 24 months of age with suspected serious infection. There will be up to 24 subjects enrolled; each will receive anidulafungin. Patients will receive anidulafungin 3 mg/kg loading dose on day 1 of study and will receive 1.5 mg/kg every 24 hours on study days 2-5.Plasma pharmacokinetics will be evaluated using a limited sampling scheme. We hypothesize that the PK parameters of anidulafungin will not differ from those observed in older children and adults.