The main dates of life and scientific and practical activity of Leopold Kasper are presented. The scientific views and thoughts of the scientist are analyzed. It is shown that after graduating in 1883 from the University of Berlin he specialized in urology under supervision of G. Thompson, P. Freyer, F. Guyon, I. Albarran and L. Dittel. L. Kasper was the founder of a large German urological school, the author of a large number of scientific works, including study dedicated to cystoscopy, endoscopic procedures, functional diagnosis of renal disorders, treatment of renal tuberculosis and urolithiasis, prostate diseases, transurethral galvanocaustics of bladder tumors, etc. He designed a special catheterization cystoscope (1895), which allowed for the first time to study differential functional ability of each kidney. It greatly facilitated the recognition and treatment of surgical pathologies of kidneys and upper urinary tract. In addition, L. Kasper improved and implemented into practice a functional renal test with fluoridzine and cryoscopic examination of urine obtained from each kidney separately after ureteral catheterization.