Drivers alerted police to a man stumbling into traffic in Lee's Summit around 7:30 p.m. on Saturday evening.
By the time emergency crews arrived at scene, the man had collapsed dead by the inner median.
A police spokesman said authorities believe the incident was a stabbing. The man's truck was found on the shoulder of the highway across from where his body was found.
Witnesses told police they saw two men fighting beside the roadway.
Lee's Summit Police said they would continue to investigate the incident, which occurred near northbound M-291 Highway near the I-470 merger.
Northbound lanes of 291 Highway near Colbern Road and northbound lanes of I-40 past Douglas Street closed for hours as police investigated the scene.
Police are asking anyone who has information about the incident to call Lee's Summit police at 816-969-7390.