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.

Inclusion Criteria:

• Age < 24 months at the time of enrollment
• Patient must have sufficient venous access to permit administration of study medication
• Infant or toddler suspected to have a serious infection and from whom a blood culture has been obtained with 48 hours of study entry
• Availability and willingness of the parent/legally authorized representative to provide written informed consent.

Exclusion Criteria:

• Patients with a history of anaphylaxis attributed to an echinocandin
• Any other concomitant condition, which in the opinion of the investigator would preclude a patient's participation in the study
• Previous participation in this study
• Previous exposure to an echinocandin in the month prior to study.