DOTC was studied experimentally and clinically, and the following data were obtained.
1) The MIC value of DOTC to 41 strains of pathogenic organisms was almost the same with that of TC except to 6 strains of E. coli and to 1 strain of Pseudomonas.
2) The concentration in the blood and urinary exc retion of DOTC were studied after an oral administration of 200 mg of DOTC. The former reached to 3. 1 mcg/ml the highest after 2 hours, and decreased gradually until' 24 hours, and the latter excreted 20. 1 % of administered drug in urine within 24 hours.
3) DOTC was clinically applied to 13 cases of simple cystitis and 22 cases of complex cystitis by three methods of administrations: A is initially 200 mg and successively 100 mg, B consists of 100 mg every day and C 100 mg every 12 hours.
4) Three methods gave a remark able effect in the treatment of simple cystitis, but the ineffective cases of 59. 1 96 were experienced in complex cystitis.
5) DOTC is recommendable especially in th e treatment of E. coli, Klebsiella, and each cocci, but not in Proteus, Pseudomonas, Paracoli infections.
6) No significant side effect was obse rved.