We describe a case of peritonitis due to Verticillium spp. in a 33-year-old farmer on continuous ambulatory peritoneal dialysis (CAPD) for 3 months for end-stage renal failure due to chronic pyelonephritis. The etiologic agent was a hyaline hyphomycete which we report as a new human opportunistic pathogen. The fungus was isolated from the peritoneal fluid culture and from the tip of the catheter; identification was made on the basis of macroscopic and microscopic features. The patient had previously been admitted to our hospital for peritonitis caused by mixed enteric flora and treated for 8 days with intraperitoneal broad-spectrum antibiotic therapy. Five days after discharge he was readmitted for severe abdominal pain and cloudy drainage fluid. Two days of intraperitoneal broad-spectrum antimicrobial therapy produced no clinical improvement. Intravenous fluconazole and oral flucytosine were administered upon identifying the fungus. After another 2 days without improvement, peritoneal dialysis was discontinued and the catheter removed. Antimycotic therapy was continued for 4 days with complete resolution of the peritonitis. The patient chose to start hemodialysis and was discharged in good clinical condition.