Any method of drug administration that avoids the gastrointestinal tract is termed parenteral administration. Transdermal, intranasal, rectal are therefore parenteral methods. However, the usual term parenteral is reserved for drug injections. They can be employed in an unconscious or an uncooperative patient. They can be employed in cases of vomiting and diarrhea and in the patients unable to swallow. Drugs which might irritate the stomach or which are not absorbed orally can be administered, e.g. aminoglycosides. Strict aseptic precaution should be taken while giving injection in order to prevent infections due to HIV and hepatitis B virus. Disposable syringe and needle should be used and should be purchased from an authentic source. Parenteral, parenteral—intramuscular, parenteral—subcutaneous, parenteral—intradermal injection, parenteral—sublingual, and parenteral—transdermal are also discussed in this chapter.