The clinical efficacy of micafungin (MCFG) in surgery, emergency, and intensive-care medicine has been studied in only a limited number of cases. We conducted a multicenter postmarketing study to evaluate MCFG efficacy and safety in Japan. MCFG was given to patients with a temperature exceeding 37.5 degrees C, either with a proven fungal infection based on mycological or histopathological examination, or those who were regarded as having probable or possible fungal infections (patients who had at least one high-risk factor for the development of a systemic fungal infection and for whom fungi had been detected at multiple sites by surveillance culture or a positive beta-D-glucan test). Efficacy was evaluated using the AKOTT algorithm created by our group (AKOTT is an acronym created from the first letter of the surname of each of the five members of the evaluation committee). Of the 180 patients enrolled, 68 were excluded by exclusion criteria or for other reasons, and 112 (58 with proven candidiasis, 1 with proven aspergillosis, and 53 with suspected fungal infection) were evaluated for efficacy. MCFG was administered at a mean daily dose of 104 mg for a mean duration of 14.2 days. It was effective in 72 p 72 patients, ineffective in 28, and the effect was undeterminable in 12, for an overall clinical efficacy 72.0%. MCFG was effective in 78.6% of those with proven candidiasis and in 65.1% with suspected fungal infection, but it was ineffective in the 1 patient with aspergillosis. MCFG eradicated 77.6% (52/67) of fungi isolated. There were 69 drug-related adverse reactions, mainly abnormal hepatic function tests, in 37 of 178 patients evaluated for safety. One adverse reaction, skin eruption, had a probable causal relationship with drug treatment. In conclusion, MCFG had high clinical efficacy and safety in the treatment of deep-seated fungal infections in surgery, emergency, and intensive-care medicine, indicating good potential as a firstline drug for both targeted and empirical therapies.