Nearly 23 million people tuned in to Monday night's premiere of CSI: Miami on CBS, making it the most-watched September drama debut since ER in 1994.

It was a promising start, even for a show most analysts expected to do well. CSI: Miami is a sun-soaked spinoff from the popular CSI: Crime Scene Investigation and stars David Caruso and Kim Delaney.

The debut was good news, too, for David Letterman. The CBS late-night host has complained that his ratings were hurt by a relatively weak crop of CBS programs at 10 p.m. ET, so CBS made fixing that hour a priority this fall.

Letterman scored his highest ratings for a Monday night episode this week since last December, Nielsen Media Research reported Tuesday.