The body was found Wednesday morning near the corner of Avenue Seven and Road 34.
An autopsy was inconclusive, and investigators have been unable to identify him.
They released a composite sketch of the victim hoping someone will know who he is.
The man was five-feet-8-inches tall and weighed about 160-pounds. He had brown eyes and a goatee.
Investigators also say he was missing several teeth and had what's called "cauliflower ear" on his left ear, a condition linked to boxing or possibly from a fight.
Anyone who recognizes the man is asked to call the Madera County Sheriff's Office.