Dimension X was an old-time radio program broadcast April 1950 to September 1951 on NBC and were written by famous science fiction authors at the time.
Dimension X was the first notable adult science fiction series on radio, preceded only by the short-lived 2000 Plus, scattered episodes of anthology dramas, and juvenile fare, such as Flash Gordon.
The series featured adaptations of stories by respected science fiction writers such as Ray Bradbury, Isaac Asimov and Robert A. Heinlein. The first thirteen episodes were broadcast live, the remainder prerecorded.
Dimension X lasted only one year, but the later X Minus One utilized many of the same actors and scripts. All fifty episodes survive and are available from various retailers.
To listen to some Dimension X shows for free, click any of the links below.
1950-12-24 The Green Hills of Earth
For more information about this show, please visit Wikipedia's Entry, which is where most of the above was sourced or see the episode list at OTRSite