Chemotherapy is the use of drugs to treat cancerous cells. Chemotherapy can be administered intravenously (in the vein) or by pill, and usually involves a combination of drugs. Chemotherapy treatments are often given in cycles: a treatment period, followed by a recovery period, followed by another treatment period. Chemotherapy may be given in a variety of settings including your home, a hospital outpatient facility, a physician's office or clinic, or in a hospital. Hospitalization may be necessary to monitor treatment and to control chemotherapy's side effects.