Co-written by Polanski and Gerard Brach, "Repulsion" follows an escalating dove-tailing story form that Polanski explored in his later "apartment" films "Rosemary's Baby" and "The Tenant."
This was, in fact, something Polanski would return to—with himself in the title role—in The Tenant (1976).
Repulsion, Rosemary's Baby, and The Tenant are often loosely linked as Polanski's "Apartment Trilogy", scary films about the life of urban renters.
It's certainly tempting to look at Repulsion as an answer to Psycho (released five years before) and as a warm-up for Polanski's The Tenant and Rosemary's Baby, with their hemmed-in apartments and batty old neighbors (and limber, free-form camera work).
The neighbours in The Tenant share their blood lust.
Though the story of an immigrant (Polanski) being driven insane as he gradually transforms into the previous tenant of his overpriced Parisian apartment has a certain affinity to Polanski’s earlier film Repulsion (1965), the core of The Tenant is about the casual persecution of a foreigner in a strange land for no other reason than the fact that he is a foreigner.