Although often referred to as a "debunker", Randi has said he dislikes the term's connotations and prefers to describe himself as an "investigator". He has written about paranormal phenomena, skepticism, and the history of magic. He was a frequent guest on The Tonight Show Starring Johnny Carson, famously exposing fraudulent faith healer Peter Popoff, and was occasionally featured on the television program Penn & Teller: Bullshit!
Prior to Randi's retirement, JREF sponsored the One Million Dollar Paranormal Challenge, which offered a prize of one million dollars US to eligible applicants who could demonstrate evidence of any paranormal, supernatural, or occult power or event under test conditions agreed to by both parties. The paranormal challenge was officially terminated by the JREF in 2015. The foundation continues to make grants to non-profit groups that encourage critical thinking and a fact-based world view.