The concept of intraoperative in vivo diagnosis and selective resection of infiltrated lymph nodes in ovarian cancer has not been evaluated despite the increased morbidity associated with pelvic and paraaortic lymph node dissection and its questionable therapeutic value. Fluorescence photodetection is based on the application of a photosensitizer relatively selective for malignant tissue, which after light activation of appropriate wavelength, shows fluorescence. Six hours after oral application of 10 mg/kg body weight 5-aminolevulinic acid, the abdominal cavity of a patient with suspicion of recurrent ovarian cancer was inspected using a laparoscope and blue light at 380-440 nm. Spectral measurements at a wavelength of 635 nm, multiple peritoneal biopsies, and lymph node excisions were performed. White light inspection and porphyrin fluorescence photodetection revealed no intraperitoneal metastases and multiple biopsies were negative. Fluorescence-positive lymph nodes were visible only in the left common iliac region and a specific porphyrin fluorescence peak could be detected. In contrary, no increased porphyrin fluorescence of intraperitoneal tissues or skin was seen. Fluorescence microscopy showed the characteristic red fluorescence in the infiltrated parts of the lymph node tissue by the papillary ovarian cancer. Histology of the other sites was negative. No systemic or cutaneous side effects were recorded. This data is a proof of the concept that porphyrin fluorescence-guided lymph node metastasis detection is possible in ovarian cancer and should stimulate further research in this field.