Cancer of the bladder is not a single disease. It encompasses a spectrum of neoplasia which ranges from a benign papillary growth of slow and recurrent course to a highly invasive and aggressive anaplastic tumor of short duration and rapid lethality. Among some authors, there is a tendency to paint the clinical picture in either black or white; others dwell on the chiaroscuro of tones, noting the variability of duration, different types of presentation, different locations, and multiplicity of lesions. The disparity of results with the numerous treatment methods which are documented will leave the careful reader with the impression that either reported series differ in composition more than their descriptions reveal, or that all of the facts are not being presented. The search for some measurable characteristic which is common to all of these tumors and which would allow accurate prognostication occupies the attention of many investigators.