Paul Ehlrich was the German Biologist who discovered chemotherapy.The person who discovered chemotherapy is known as father of chemotherapy. He was doing his research in the field of immunology and chemotherapy that was when was chemotherapy discovered in 1940 .The German biologist who discovered chemotherapy discovered accidentally ,observed the autopsy of people being exposed to mustard gas. Mustard gas which was used for chemical warfare had the unique characteristic of suppressing the leukemia and lymphoma. Paul Ehlrich who discovered chemotherapy took the first step to use chemicals to treat cancer. In late 1940’s the United States Department of Defense recruited Louis S.Goodman and Alfred Gillman for further studying the chemotherapy treatment and they were the persons chemotherapy first invented. The results of their study were successful. They initially found that it was good for treating lymphoma. Later in 1965 James Holland, Emil Freireich, and Emil Frei arrived at a result that chemotherapy could be a better treatment than other cancer treatments. Today more than 50 percentage of cancer patients seek chemotherapy treatment.The invention of chemotherapy has many patients diagonised of cancer to seek treatment and those at early stages successfully recover from the disease .If the growth of cancer cells are large and if it is not possible to recover fully ,chemotherapy helps such patients by preventing the division of the cells further and extending their lifetime.