A 41-year-old woman on continuous ambulatory peritoneal dialysis (CAPD) presented with algal peritonitis. Prototheca wickerhamii was isolated from multiple dialysate effluent cultures. Despite treatment with amphotericin B, catheter removal was required. An attempt to reinsert a Tenckhoff catheter 3 months later was unsuccessful because of dense intraperitoneal adhesions. Prototheca sp are a rare cause of human disease, this being the first reported case of algal peritonitis complicating CAPD.