As many critics noted (not always approvingly), Stanley Donen filmed this thriller in an uncharacteristically flamboyant style, using bizarre camera angles and eccentric visual compositions throughout. He later admitted that he had never felt that the screenplay was quite right (Many writers worked on it, and it was rumored to be still being reworked during shooting). So, he had given the film an unusual look to disguise its shortcomings. He had had to start filming before he was ready, in order to accommodate the busy schedules of Gregory Peck and Sophia Loren.
The part of David Pollock originally was written for Cary Grant. When Gregory Peck had trouble getting the humor right in a line, he'd smile and tell director Stanley Donen, "Remember, I'm no Cary Grant."
An interesting note is that this movie is the first in the career of stunt man Vic Armstrong, who is listed in the Guinness Book of World Records as the World's Most Prolific Stunt Man. He began his career as Gregory Peck's horse-riding stunt double on this movie.
Gregory Peck found the stunts particularly difficult because of an old leg injury due to horseback riding. During the escape in the corn field, Peck had to keep telling Sophia Loren to slow down because it looked as if she was rescuing him and not the other way around.
A sequence involving eye drops being dropped into an eye was donated by Stanley Donen to the Johns Hopkins Medical School 'Ophthalmic Division' for research purposes.