Director Sam Peckinpah was in ill-health throughout the shoot. The long-term toll of his drug and alcohol abuse suggested to many in the production that he was dying. Peckinpah would go off and take opportune naps, but still completed and delivered his initial cut of this movie on time, despite sickness and exhaustion.
Several cast members who worked on this movie, such as Sir John Hurt, Dennis Hopper, and Burt Lancaster, took lower salaries, so they could work with legendary Director Sam Peckinpah.
The mustache that Craig T. Nelson wore throughout this movie was glued on. Sam Peckinpah apparently hated it, and would rib Nelson constantly about it during the shoot.
No damage, special effects, or action work was meant to be done at Robert Taylor's former ranch residence, the filming location for the house seen in the movie. But the production just went ahead, and shot out windows, conducted a poolside shoot-out, and damaged the swimming pool.
According to the documentary Alpha to Omega: Exposing 'the Osterman Weekend' (2004), Sam Peckinpah hated Robert Ludlum's novel, and he did not like the screenplay for the movie either. But regardless of his dislike for the book, Peckinpah still accepted the director's job, as he was desperate to re-establish his legendary director position within the Hollywood film community.