In 1982 he began a killing spree that spanned two and a half years. It is believed that he murdered 50 women most of which were either prostitutes or teenage runaways that he picked up along Pacific Highway South. Once murdered, the bodies were usually dumped along or near the Green River in Washington. Two victims, however, were found in Portland, Oregon.

Ridgway was arrested twice, once in 1982 and again in 2001 for cases of prostitution. In 1983 he became a suspect for the Green River Killer and in 1984 he took a polygraph test that he subsequently passed.

On April 7, 1987 police took hair and saliva samples that were used for a DNA test that was later used in order to arrest him. On November 30, 2001, nearly 20 years later, Ridgway was arrested for the murders of four women that his DNA connected him too.

On November 5, 2003 Ridgway pled guilty to 48 counts of aggravated first degree murder. His plea spared him from being executed for the murders as long as he led officials to the bodies of the murdered women and gave them additional details that they asked for. There is much controversy over whether or not this was the right approach. Many feel that he should have been executed.

On December 18, 2003 he was convicted to 48 life sentences without possibility of parole and one life sentence to be served consecutively.

The TV miniseries, The Capture of The Green River Killer tells the story of the Green River Killer. Tom Cavanagh stars as Dave Reichert, the sheriff who was in charge of the Green River Killer case.