To the Editor: The article on Industrially Acquired Porphyria in the JuneArchives of Dermatologyby Dr. Bleiberg and associates was very interesting. However, I am puzzled by two matters. There were frequent statements to the effect that the Watson-Schwartz method was used for detecting urinary and fecal uroporphyrin and coproporphyrin excretion. This is exceedingly puzzling as the Watson-Schwartz test is a test for porphobilinogen and not uroporphyrin or coproporphyrin. I would be most interested to learn just what test was used for screening for uroporphyrin and coproporphyrin. This point is not idle carping, as porphobilinogen excretion is usually completely normal in those cases of porphyria with cutaneous symptoms. Most cases of cutaneous porphyria would be missed if the Watson-Schwartz test were relied upon as a screening procedure. Secondly, I am puzzled why a study from a metropolitan area did not employ quantitative methods of measuring porphyrin excretion. The experts