Pasolini co-wrote the screenplay of Ostia with director Sergio Citti, who had been Pasolini's script assistant on Accattone and Mamma Roma, and his assistant director on a number of films, including The Hawks and the Sparrows and Teorema. In Oswald Stack's Pasolini on Pasolini, he calls Citti “my oldest friend in Rome.... He helped me enormously in all my novels, he was like a living dictionary for me...(for) the jokes and the local slang of the Roman characters, in which he was extremely proficient.” Pasolini chose Citti's younger brother, Franco, to play the lead in Accattone, and later to play in Mamma Roma. Franco Citti stars in Ostia as one of two naively anarchistic brothers who earn their living as petty thieves but whose battles with the world and ultimately with each other have a religious aspect to them--as Variety's Gene Moskowitz put it, “a smattering of Cain and Abel.”
“Citti displays the Pasolini world of almost Biblical resonance and parable foisted on a table of subproletarian life,” writes “Mosk". “Reminiscent more of Pasolini's Accattone than his later more arty and artful films, Ostia indicates that Citti has a more poetic, muted filmic flair than is usually connected with Pasolini.”