ABC’s “Jimmy Kimmel Live” continues to gradually build its audience, this spring racking up the show’s most-watched quarter in its nearly 10-year history.

“JKL” was the only latenight program to average more viewers both vs. its first-quarter performance and vs. the second quarter of 2011, according to Nielsen. Its lead-in, “Nightline,” was again the most popular latenight program.

Also of note for the quarter, NBC’s combo of Leno and Fallon opened up some distance on the CBS tandem of Letterman and Ferguson vs. their matchup in the winter.

Looking at the numbers, “Jimmy Kimmel Live” averaged 1.86 million viewers during the quarter that ran from March 26-June 24 — up 4% from the second quarter of last year (1.79 million) and 9% larger than this year’s first quarter.

This is the most-watched quarter for “JKL” since it bowed in January 2003.

Among all programs for the quarter, the total-viewer standings had “Nightline” (3.84 million) followed by NBC’s “Tonight Show with Jay Leno” (3.51m), CBS’ “Late Show with David Letterman” (2.85m), Comedy Central’s “Daily Show” (2.15 million) and “Jimmy Kimmel Live” (1.86m). This marks the seventh straight quarter that “Nightline” has ruled as the top latenight show in total viewers, and it has also been No. 1 among adults 25-54 for six of the past seven quarters.

And in adults 18-49, “Nightline” (1.20 million) narrowly led “Daily Show” (1.19 million). They were followed by “Tonight Show” (1.00 million) and “Late Show” and “Colbert Report” (both 0.90 million). “JKL” moved up to sixth (707,000), ahead of NBC’s “Late Night With Jimmy Fallon” (660,000), which is hurt in such comparisons by starting 35 minutes later than Kimmel (12:37 a.m. vs. 12:02 a.m.).

NBC could point to larger quarterly head-to-head advantages over CBS. “Tonight Show” increased its lead over CBS’ “Late Show” by 11% in adults 18-49 viewers (999,000 vs. 896,000), up from 4% in the first quarter. And in total viewers, the gap of 23% was larger than the first quarter’s 16% advantage.

And at 12:35 a.m., “Late Night” increased its lead over CBS’ “Late, Late Show with Craig Ferguson” to 26% in 18-49 viewers (660,000 vs. 525,000), up from 17% in the first quarter.