By the late 1960s, Assonitis began producing films himself with the documentary The Labyrinth of Sex and the giallo thriller Who Saw Her Die?
The film is the first of the subgenre of Italian Cannibal movies that were made in the late 70s and early 80s[6][7][8][9] The following year, Assonitis produced The Last Snows of Spring.
The film obtained a great commercial success, particularly in the United Kingdom and launched the career of child actor Renato Cestiè.
Assonitis' sophomore directing effort came after the tremendous box office success of Jaws, when he and American International Pictures produced Tentacles.
The film was directed by Giulio Paradisi and featured another all-star cast, including John Huston, Shelley Winters, Mel Ferrer, Glenn Ford and Sam Peckinpah with a cameo appearance by Kareem Abdul-Jabbar and an uncredited Franco Nero in the prologue.
[18] On Metacritic, the film has a weighted average score of 65 out of 100, based on 5 critics, indicating "generally positive reviews".
The same year, Assonitis was brought in by Warner Bros. to executive produce Piranha II: The Spawning, replacing Jeff Schechtman.
In 1987, Assonitis signed a multi-picture deal with Trans World Entertainment, then run by Moshe Diamant and Eduard Sarlui.
[24] Over the next two years, Assonitis produced three more pictures under the deal: Sonny Boy, starring Paul L. Smith, David Carradine and Brad Dourif; The Bite and Amok Train.
Universal acquired the rights and remade the film as Scent of a Woman starring Al Pacino and directed by Martin Brest.
Assonitis, who had originated the project and chose to go uncredited on the final cut of the film, took out a full page advert in Variety congratulating Tom Pollock, Universal Pictures and Martin Brest for making the adaptation successful and praising Al Pacino on his Oscar win.
The festival opened with a theatrical screening of Tentacles and also conducted a retrospective of his films including Who Saw Her Die?, Beyond the Door, The Visitor, Madhouse and Piranha II: The Spawning.
[41] Assonitis was the recipient of the Time Machine Award from Sitges Film Festival in October 2024 for his multifaceted career and his fundamental role in the development of Italian cinema since the 1960s.