The show on Thursday (5 November) will examine the growing trend for superstores to sell cut-price flat-pack bicycles.
It will follow five people as they try to build and ride self-assembly bikes bought from Argos, Asda, Halfords, Tesco and Toys R Us.
Host John Humphrys will be joined by South Coast Bikes' Paul Topham and our own John Stevenson as he looks at the rise of the 'Bicycle Shaped Object' (BSO).
"It's easy for us bike geeks to be snotty about cheap bikes," said John Stevenson. "But I'd be amazed if anyone watching this show isn't convinced that they really are a bad way to spend your money."
The show airs at 8pm on BBC1. Watchdog are keen to hear from anyone who has bought a 'bike in a box' – email email@example.com.
BikeRadar's John Stevenson will give his opinions on the BBC's Watchdog programme