The credits claim that Leigh Brackett's screenplay for 1967's "El Dorado" is based on a novel, "The Stars in Their Courses" by Harry Brown. The on-screen evidence indicates it was based on Brackett's own script for 1959's "Rio Bravo," in which John Wayne is a gunfighter joined by his buddy, a drunken sheriff, in guarding a town against a corrupt cattle baron. They are joined by a callow but dangerous youth, and a curmudgeonly deputy. In "Rio Bravo," these roles were admirably filled by Dean Martin, Ricky Nelson, and Walter Brennan. In "El Dorado," the Duke once again takes on the gunfighter role, but is joined this time by Robert Mitchum, James Caan, and Arthur Hunnicutt. Nothing wrong with that lineup, even though Caan can't sing like Ricky (Mitchum could probably do a fair imitation of ol' Dino, though). Like "Rio Bravo," this one is directed by Howard Hawks who liked to steal from his own movies. Several scenes in "El Dorado" are nearly exact duplicates of moments from "Rio Bravo" (Mitchum blasts holes into a piano when he suspects that the pianist's off-key playing denotes fear of the killer hidden behind it, whereas Martin found his prey in a saloon balcony after spotting blood dripping into a shot glass).
"El Dorado" is faster paced than the first film, but then it has a shorter running time. It's a pleasure through and through, but "Rio Bravo" is superior. In the latter film, you almost feel that you're holed up with the Duke, Dino, Ricky, and Walter, rather than just watching them.