Runyon almost totally avoids the past tense (it is thought to be used once, in the short story "The Lily of St Pierre", and once in "The Idyll of Miss Sarah Brown" ), and makes little use of the future tense, using the present for both. He also avoided the conditional, using instead the future indicative in situations that would normally require conditional. An example: "Now most any doll on Broadway will be very glad indeed to have Handsome Jack Madigan give her a tumble ..." (
Guys and Dolls, "Social error"). There is an homage to Runyon that makes use of this peculiarity ("Chronic Offender" by Spider Robinson) which involves a time machine.
He uses many slang terms (which go unexplained in his stories), such as:
- pineapple = pineapple grenade
- roscoe/john roscoe/the old equalizer/that thing = gun
- shiv = knife
- noggin = head
- snoot = nose
There are many recurring composite phrases such as:
- ever-loving wife (occasionally "ever-loving doll")
- more than somewhat (or "no little, and quite some"); this phrase was so typical that is was used as the title of one of his short story collections
- loathe and despise
- one and all
Runyon's stories also employ occasional rhyming slang, similar to the cockney variety but native to New York (e.g.: "Miss Missouri Martin makes the following crack one night to her: ‘Well, I do not see any Simple Simon on your lean and linger.’ This is Miss Missouri Martin’s way of saying she sees no diamond on Miss Billy Perry’s finger.” (from "Romance in the Roaring Forties").
The comic effect of his style results partly from the juxtaposition of broad slang with mock-pomposity. Women, when not "dolls", "Judies", "pancakes", "tomatoes", "broads" or what have you, may be "characters of a female nature", for example. He typically avoided contractions like "don't" in the example above, which also contributes significantly to the humorously pompous effect. In one sequence, a gangster tells another character to do as he's told, or else "find another world in which to live."
Runyon's short stories are told in the first person by a protagonist who is never named, and whose role is unclear; he knows many gangsters and does not appear to have a job, but he does not admit to any criminal involvement, and seems to be largely a bystander.