One important theme in organic synthesis is to accomplish highly selective transformations under mild conditions, which yield only desirable products. During the past two decades, we have developed several useful tools to achieve this, i.e., organochromium reagents. This review focuses on the following themes: 1) The historical background of organochromium reagents. 2) The development of the allylic chromium reagent (Nozaki-Hiyama reaction). 3) Nickel-catalyzed addition of alkenyl-, aryl-, and alkynyl halides to aldehydes (Nozaki-Hiyama-Kishi (NHK) reaction). 4) Wittig-type olefination with geminal dichromium reagents. 5) Representative applications of organochromium reagents to the total syntheses of biologically active compounds.