We identified candidate flux ropes by using interplanetary magnetic field data obtained by the Wind spacecraft and selecting the periods when the third derivative of each interplanetary magnetic field component with respect to time was continuously smaller than a certain value. If the data gathered during these periods fit a cylindrical force-free field model, the candidates were classified as flux ropes. There were too many flux ropes that had a large impact parameter value to be explained by the finite lengths of the flux ropes (or possibly the curvatures of the flux rope axes). We thus excluded flux ropes having a large impact parameter value from our analysis of fitted parameters. We took into account short-duration flux ropes (2--10 hours), and we found that the number of small flux ropes is much larger than that of large ones. We found that this method works well in identifying flux ropes provided that valid criteria have been established. ¿ 2000 American Geophysical Union