Five recent decisions of the United States Supreme Court, together with a decision of the United States Court of Appeals for the Third Circuit, have considerably changed some of the currently accepted theories regarding the taxability under the Federal Estate Tax of transfers reserving various degrees of control to donors, both with respect to what may be considered to be a sufficient reserved control and what the constitutional limits on the taxing power may be. Some perplexing questions have been settled by these decisions while others quite as vexing seem to have been raised and left for future determination.