Hospital emergency codes, or codes, are used to alert staff in a myriad of emergency situations. They are designed to convey essential information as quickly and with as little confusion as possible whilst also remaining discreet in order to keep both patients and visitors calm. They may be posted in signs around the hospital or on the back of employee identification cards for reference.

In general, the codes are based on a color system, though there are also codes with numbers and names. These codes may be different from hospital to hospital, but there is a movement to standardise the code for easy access and to avoid the wrong command being followed.

Because of the large variations within the system, the following are only the most pertinent or those used on House.