We all know that washing hands is an important act of personal hygiene to protect us from infections with microorganisms. Is there any published evidence that washing hands does any good? In this article we briefly examine studies by Ignaz Semmelweis that show its importance. This work is an early contribution to the germ theory of disease. At the end of the article, there is an experiment demonstrating the evidence of his antiseptic practice. Until the middle of the 19th century, hand washing by physicians and students was hasty and superficial (Slaughter 1950). They washed their hands with tap water and dried them on their handkerchiefs or waved them in the air; the surgeons then went directly to the wards to examine patients. Doctors believed in the miasma theory of disease. This theory blamed epidemics on some peculiar change in the atmosphere that was produced by poor sanitary conditions (Dowling 1977). Puerperal (pertaining to or connected with childbirth) or childbed fever was believed to be an illness of miasmatic origin, but no one felt responsible for the atmospheric influences or capable of coping with them. Childbed fever was an ancient scourge. The heroine in Tolstoi's novel Anna Karenina suffered from the disease. The illness was described in general terms, yet was unmistakable (Sigerist 1943). The New York Hospital had to close its obstetric service in 1828 because of the high death rate due to childbed fever. Eleven years later, a famous New England physician, Oliver Wendell Holmes, stated that childbed fever was probably carried by doctors from ill to healthy expectant mothers. He also proposed that the disease was passed from autopsy to bedside. He advised physicians to change their clothes and wash their hands and fingernails with a solution of calcium chloride before examining patients (Harbert 1980). These new ideas met with a great deal of opposition from obstetrics professors all over America. But no one knew the cause of childbed fever. We now know that the disease usually is due to infection with the bacterium Streptococcus pyogenes. It infects the patient, reproduces rapidly and causes a serious, oftentimes fatal, infection in mothers who have just given birth (Wilson 1955). Streptococcus pyogenes was discovered in the late 19th century. The bacterium Staphylococcus areus also has caused the disease. This information was unknown until the 1880s and Louis Pasteur's statement of the germ theory of disease. In 1848, a young Hungarian physician, Ignaz Philipp Semmelweis, began to practice handwashing as an antiseptic measure in the obstetrics clinic of Vienna. Semmelweis (Figure 1) received his medical degree from the University of Vienna in 1844 and shortly after that attained the degree of master of midwifery (Robinson 1929). Medical students routinely examined patients in the First Clinic in Vienna. In the Second Clinic, the midwives were trained and held responsible for patient care. Childbed fever raged in the First Clinic, with a mortality rate of about 10 percent-four times as great as that of the Second Clinic. Semmelweis knew the midwives did not attend autopsies. Nor did they do patient examinations as frequently as the medical students. It was appalling that more women were dying in the hospital attended by physicians than those attended by midwives. One of Semmelweis's teachers died suddenly from a small wound received while performing an autopsy. Semmelweis realized that the pathologic changes in the death were identical to those of women dying of childbed fever. During this time Semmelweis, his students and physicians were examining the birth canals of female patients with unwashed hands after they came directly from the autopsy rooms (Gyorgyey 1968). The doctors and students were the instruments of death and carried cadaver particles on their unwashed hands from the autopsy room directly to the patients (Sinclair 1909). In May 1847 Semmelweis began a plan to destroy the poison carried from cadavers and sick patients by