A portable anesthetic machine comprises a chassis having a cradle which removably receives a vaporizer, a control panel and a support member. The control panel and support member are pivotal relative to each other to selectively change the machine between carrying and use configurations. The control panel includes a gas flow path having gas inputs connectable to sources of carrier gases, a manifold which combines the gases, a carrier gas outlet and inlet connectable to the vaporizer input and outlet, respectively, a common gas port, and flow control devices to control the carrier gas flow rate and to control the anesthetic and carrier gas mixture. A controller is also provided which controls the flow of gas into and around the vaporizer to maintain a substantially constant concentration of anesthetic agent in the gas stream delivered to the patient without the need to adjust the flow of gases from the gas supply sources.