The Museum of Modern Art is introducing timed-entry tickets today for its highly popular exhibition "Picasso and Portraiture: Representation and Transformation," which has been drawing crowds since it opened on April 28.

Entrance to Prehistoric Journey is included with museum admission, but a separate timed-entry ticket is required, and reservations are strongly recommended.

Through Sunday, admission to "The Butterfly Conservatory" is free, but timed-entry tickets are required.

Admission to both is by timed-entry ticket only, available on the half-hour beginning at 10 a.m.; entry to "The Butterfly Conservatory" is every 15 minutes.

Through Jan. 27, admission to "The Butterfly Conservatory" is free every weekend, but timed-entry tickets are required.

With its stark wartime artifacts and mixed-media exhibitions, the museum has proved so popular, particularly with World War II veterans and their families, that it issues timed-entry tickets to ease the flow of 1,300 visitors a day.

Tours of Ford's Theatre and the adjacent Petersen House are by timed-entry ticket.

Admission to the Butterfly Conservatory and "Baseball as America" is by timed-entry ticket only, available on the half-hour beginning at 10 a.m. (Butterfly Conservatory, every 15 minutes).

Like the rest of the public, Ms. Gillespie went to the Ellipse and stood in line through the night to get free, timed-entry tickets from the National Park Service for the roll.

I had called ahead to buy timed-entry tickets for the 17-minute multimedia orientation program, "Freedom Rising," presented in a 350-seat steeply banked theater in the round.