In the old time radio community, the episodes listed below are usually regarded as some of the finest examples of how horror was achieved on radio.
(I've only put them in date order, you can decide for yourself which are the scariest.)
"The House in Cypress Canyon" (1945) - Suspense
"Death Robbery" starring Boris Karloff (1947) - Lights Out
"The Thing on the Fourble Board" (1948) - Quiet, Please (Episode most often picked as the scariest of them all.)
"Ghost Hunt" (1949) - Suspense
"Three Skeleton Key" (1949) - Escape
"Behind the Locked Door" (1951) - The Mysterious Traveler
Like this group of superb radio performances by Boris Karloff in which he mainly portrays a deranged husband.
Old time radio adaptations of "The Tell-Tale Heart" by Edgar Allan Poe.
Resurrecting the Dead on Radio - various shows dealt with the idea of bringing the dead back to life.
Most gruesome true story that Suspense tried to dramatize on radio: "Neil Cream, Doctor of Poison"
Most gruesome true story that Lights Out tried to dramatize on radio: "Murder Castle"
Suspense's take on the Lizzie Borden story: "Fall River Tragedy/Goodbye, Miss Lizzie Borden"
"Sorry, Wrong Number" - Agnes Mooreheads performed Suspense's classic story eight times.
Our other favorite creepy and scary episodes:
"A Knock at the Door" (1942) from Lights Out
"The Gibbering Things" (1943) from The Shadow
"Call Her Jean (a.k.a. "It Happened")" (1938) from Lights Out
One of the favorite supernatural stories posted on Escape and Suspense! is "Bells" (1961) from Suspense.
Another creepy episode from late in the Suspense series is the story/cautionary tale of "The Sin Eater" (1962).
"I Saw Myself Running" (1953) from Escape
"Chicken Heart" from Lights Out, and Bill Cosby's monologue about listening to this episode as a child.
"The Dark" is often remembered for its grossness and wet rubber glove sound effects.
"Earth Abides" (1950) and "The Scarlet Plague" (1954) The radio versions aren't as good as the original texts, but hopefully they will guide you towards reading these early classics of disaster: Earth Abides (1949) a novel by George Stewart and the short story "The Scarlet Plague" (1912) by Jack London. (Both of these stories are set in the San Francisco Bay Area.)
We'll keep updating this page as we go along...