CCTV images have been released off a man believed to have exposed himself on a bus travelling from Lichfield to Burton.
Police say the incident happened on the X12 service at around 8.35am on July 2.
The suspect, who is believed to be aged in his 50s, left the bus in the Burton area.
Anyone with information is asked to contact PC Bryn Jeavons at Staffordshire Police on 101, quoting incident number 447 of July 4.