Before revision:  In this paper we give results for the valid inference of a treatment effect after selecting from among very many control variables and the estimation of instrumental variables with potentially very many instrumentswhen post- or orthogonal L_2-Boosting is used for the variable selection.
After revision:  In this paper we give results for the valid inference of a treatment effect after selecting from among very many control variables and instrumental variable models with potentially many instruments. To achieve this, we establish new results for the rate of convergence of iterated post-L_2-Boosting and orthogonal L_2-Boosting is used for the variable selection.