Serum protein-bound fucose rose significantly in a high percentage of patients with advanced cervical and ovarian cancer, whereas no increase was found in patients with benign gynecologic disorders. Serum fucose levels were not influenced by precedent therapy and correlated well with the clinical stage of squamous-cell carcinoma of the cervix. This correlation was found to be exceedingly helpful in establishing the presence of and in evaluating the extent of recurrent cervical cancer.