Experimental obstruction of urethra was induced for 66 hours on 5 male dogs to determine the diagnostic value of ECG and blood chemical values. The results obtained in the examination were summarized as follows ; 1. Changes of ECG, blood chemical values and clinical sings were observed from 30 hours after urethral obstruction. 2. In ECG, the peaked and amplitude of T wave were increased remarkably. p wave were decreased, and intervals of PR(Q) and QRS complex were prolonged after urethral obstruction. 3. The levels of BUN, potassium, creatinine in serum after urethral obstruction were increased remarkably and correlation between these levels and the increase of amplitude in T wave were recognized to be significant.