The terms Primary Phase and Secondary Phase describe the first two radio series of The Hitchhiker's Guide to the Galaxy, first broadcast in 1978. These were the first incarnations of the Hitchhiker's Guide to the Galaxy franchise. Both were written by Douglas Adams and consist of six episodes each.
The series followed the aimless wanderings of Arthur Dent, Ford Prefect and his book, the eponymous Guide. It introduced unfamiliar music,[1] mind-stretching concepts and the newest science mixed together with-out of-context parodies, unfeasibly rude names, "semantic and philosophical jokes",[1] compressed prose, and "groundbreaking deployment of sound effects and voice techniques".[2] By the time the sixth episode was broadcast, the show had a cult following.[1] A Christmas special would follow, many repeats and a second series. The two original series were followed by three more in 2004 and 2005 and a final, sixth series in 2018.
The following article is a list of episodes from the Primary and Secondary Phases. For information on its production, see The Hitchhiker's Guide to the Galaxy.