Letterman went on to graduate from Ball State University in the late 1960s and married Michelle Cook in 1969. From 1970 to 1974 he worked as a weatherman and TV announcer, and from 1974 to 1975 as a radio talk show host.

As the late 1970s approached, Letterman was working as a struggling stand-up comic at The Comedy Store and started writing for television shows. He wrote for the summer series "The Peeping Times" and even for such shows as "Good Times" (1974). Letterman had become something of a minor celebrity in 1978.

Eventually, his work prompted many appearances on "The Tonight Show Starring Johnny Carson" (1962). He became so popular that he became permanent substitute host by the end of the decade. NBC saw great potential in the young irreverent comedian, so they gave Letterman his own daytime talk show, "The David Letterman Show" (1980), which was a disaster and aired for only a few months. About this time, Tom Snyder was having problems with his late night show, "The Tomorrow Show" (1973), which aired after the "Tonight Show." . Letterman, who was still permanent co-host of the "Tonight Show," took over the post-Carson slot with "Late Night with David Letterman" (1982).

Letterman would shy away from cameos and stuck almost solely to doing his "Late Night" show.

In 1993, Letterman made his own big announcement: he was leaving NBC for a lucrative contract with CBS to star in the "Late Show with David Letterman"

In recent years, Letterman has toned down his act. He dresses more conservatively and tends to go the more traditional route of talk shows. Aside from being a talk show host, Letterman is an active producer. His production company is called Worldwide Pants.