This retrospective review evaluates the response to caspofungin when given to children with febrile neutropenia and describes adverse effects attributable to caspofungin, including risk of hepatotoxicity during concomitant therapy with cyclosporine. Sixty-seven courses of caspofungin administered to 56 patients (1-17 years) were surveyed; 53 (79%) courses resulted in an overall favorable response. Ten children (15% of courses) experienced an adverse drug-related event that was probably or possibly attributable to caspofungin. Rash and hypokalemia were the most commonly identified adverse effects. One of 19 children receiving caspofungin and cyclosporine concurrently developed hepatotoxicity possibly related to caspofungin.