Stephen Colbert’s debut on CBS’ Late Show was the most-watched program in late-night last week, but NBC’s Tonight Show Starring Jimmy Fallon prevailed in the demo.

An average of 4.5 million viewers tuned in to Colbert’s premiere on Tuesday through Friday during the week ending September 11. Colbert bested NBC’s Fallon (3.9 million) and ABC’s Jimmy Kimmel Live (2 million). (Monday results are excluded due to the Labor Day holiday).

Fallon out-delivered his competitors in the 18-49 demo, with an average 1.2/6 to Colbert’s 0.9/5 and Kimmel’s 0.4/2. Among 18-34 year olds, Fallon logged a 0.7/5, tying Colbert’s 0.7/4; Kimmel logged a o.2/5.

Late Show grew 95% in viewers (4.45M from 2.28M) versus the same week last year, and 125% among adults 18-49 (0.9 from 0.4). Colbert’s Late Show also was up 250% in adults 18-34 (0.7 from 0.2) and 100% in adults 25-54 (1.2 from 0.6).

NBC noted Fallon’s weekly performance in key metrics was his best in nearly seven months.