I replicate most of the results in Angrist, Imbens, and Krueger (Journal of Applied Econometrics 1999. 14: 57-67), point to a possible error in and re-estimate Model 3. and analyze some simple extensions. The programming code, data. and results are available at http.//sites google com/site/antonnakov/software. Copyright (C) 2010 John Wiley & Sons. Ltd