The discovery of this drawing among Leonardo's papers has raised much controversy. It came to light during restoration work on the Codex Atlanticus during the 1960s.
The style is certainly in keeping with many of Leonardo's sketches but recent research indicates that the drawing is probably a late-twentieth-century hoax, and that Leonardo did not invent the bicycle after all. Leonardo's heavy black lines can generally be seen through on the other side of a page, but the bicycle parts cannot be seen in this case. It also appears the sketch was done in graphite, which was not discovered until some decades after Leonardo's death.