Objective: Establishment of a case definition for invasive candidosis in postsurgical intensive care patients. Methods: During the period of 1996-1999, 8 cases of invasive candidosis were observed on a surgical intensive care unit. Patient records were evaluated with respect to diagnostic criteria and response to antimycotic therapy. Results: Patients included 3 women and 5 men with a mean age of 62.7 (37-85) years. Candida peritonitis (n = 6) occurred after surgery or perforation of the intestinal tract, and Candida pneumonia was due to artifical ventilation (n = 3). C. albicans was isolated in all 8 cases, but mixed infections with other Candida spp. occurred in 3 cases. The Candida serum antigen test yielded a positive result in only 2/8 cases. I.v. therapy with fluconazole was successful in 7 cases, one patient with severe initial disease died with ongoing infection. With the exception of the lethal case, all patients showed a diagnostic serum antibody test, proving systemic candida infection. Conclusion: Based on the case descriptions, we propose the following definition of invasive candidosis: (1) Clinical signs of infection after surgery, (2) absence of bacterial pathogens and/or failure to respond to systemic antibiotics, (3) cultivation of Candida spp. from normally sterile sites or abundant growth in tracheal aspirate, (4) response to antimycotic therapy and (5) diagnostic serum antibody test. This definition proved to be valid for our patients and could be used as an inclusion criterion for future clinical studies of serodiagnosis of Candida infection or antimycotic chemotherapy.