A great movie,
With strong and wicked characters, my favourite with McQueen so far (Bullit might be the best known but the man has way more to offer in his filmography), directed by Sam Peckinpah who is known for some non compromising work with lots of realistic violence in his movies and this is no exception.
The kidnapping of the veterinary and his slutty wife by the psycho villain guy is more than a classic too, there ain't a dull or cheap moment in the movie.
Strongly recommended.
http://www.imdb.com/title/tt0068638/