Nitrogen-containing compounds, such as amines, imines, and enamines, are of importance not only as bulk chemicals but also as fine chemicals and pharmaceuticals. Among the various methods for the synthesis of such compounds, the simple addition of an N-H bond to a C-C double or triple bond, which is referred to as hydroamination, offers an attractive route to the synthesis of highly substituted nitrogen-containing organic molecules without the formation of any side products. Catalytic hydroamination has achieved remarkable development during the last decade. A wide variety of metals, including early- and late-transition metals, lanthanides, and actinides are currently employed in the area of catalytic hydroamination. This review summarizes the transition-metal catalyzed hydroamination of alkenes, alkynes, allenes, and 1,3-dienes. Mechanistic aspects of the reaction, which can be classified into five groups on the basis of C-N bond formation steps in the catalytic cycle, are also described.