What cases on The X Files are real?

Answer 1

No. The X Files is almost exclusively fiction. A few episodes are claimed to be based on eye-witness accounts, but there is no way of knowing if the accounts are real or how religiously the show adhered to the reports.

Answer 2

While many of the cases on The X-Files were based on urban legends none were actually real. While there were aspects to that show that seemed believable it was all a work of fiction.