The aim of the study was to describe a diagnostic protocol to lower the risk of a mycotic invasive infection among allotransplant recipients and to suggest the use of preoperative prophylaxis and/or empiric therapy. We chose a group of 268 allograft recipients with transient or constant yeast colonization or confirmed yeast infection. Among 7744 clinical samples, 475 were positive for fungi. We used conventional fungal laboratory diagnosis, enzymatic activity tests, serologic tests, molecular diagnosis of samples from sterile body sites, and histopathologic examinations. The following clinical samples were examined: blood samples; swabs from mouth lesions, throat, and rectum; and sputum, urine, and fecal samples from kidney transplant recipients and simultaneous pancreas-kidney transplantation recipients who are highly predisposed to mycotic infections. We established microbiologic criteria of a systemic mycosis and principles to distinguish colonization from infection.