Jet injection involves the use of a needle-free device that delivers a prescribed drug, vaccine, or compound intradermally, subcutaneously, or intramuscularly via high pressure produced by either a carbon-dioxide-filled or nitrogen-filled cartridge or a spring. During that procedure, the injector is held at an angle against the patient's skin, and a very fine stream of liquid medication is forced through a tiny orifice in the device, penetrates the skin in a selected volume ranging from 0.05 mL to 1.0 mL, and is deposited in the underlying tissue. When compared with methods of injection that require a needle, jet injection offers multiple benefits. It can be less painful for the patient, and it enhances compliance, reduces risks such as needlestick injuries and cross-contamination, eliminates the need for" sharps" disposal, and enables (with minimal training) the reliable, reproducible, and accurate delivery of medication. Patient convenience is also a factor: Jet injectors are designed for self-medication as well as professional use. It must be remembered, however, that treatment via jet injection is not always painless. Because of their formulations, some medications and vaccines produce a burning or stinging sensation, whether they are administered with a jet injector or a needle. Some compounded preparations, like the formulations included in this article, can be administered by jet injection, a practice that we suggest will increase in popularity as more drugs are prescribed for administration in the home setting. Because changes in drug concentration may be required to effect the transfer of an agent or ensure the accurate reconstitution of a lyophilized drug administered with a jet injector, the skill of a compounding pharmacist will be essential in preparing customized injectates. In this article, we address the use of needle-free technology in general; present examples of carbon-dioxide, spring-powered, and novel jet injection systems; and answer questions of interest to compounders about the use of jet injectors.