Dr. Walsh is best known for his pioneering work in the development of "the anatomic approach to radical prostatectomy," which involves nerve-sparing techniques that have reduced the probability of impotence and incontinence, and for his 30 years as director of the Brady Urological Institute. He has also made major contributions to the basic understanding of benign and malignant neoplasms of the prostate. Along with co-workers, he was the first to describe the 5 alpha-reductase enzyme deficiency, to develop an experimental technique for the induction of benign prostatic hyperplasia, to demonstrate the influence of reversible androgen deprivation on BPH, and to characterize hereditary prostatic cancer.