The effectiveness of artificial stocking as compared with natural propagation is one of the most fundamental problems in fish management. Recent studies show that natural spawning is much more efficient than was formerly supposed, the hatch often comparing favorably with that at hatcheries. Good results from artificial stocking have been obtained in so-called barren waters and with the use of large fish. Frequently, however, stocking has been a failure and whether it has been generally successful is still problematical. Results of some recent studies on the effects of stocking are summarized. It is believed that a major cause of the failure of stocking is the lack of complete correspondence between the ecological requirements of the fish and the environment. The great need for further studies is stressed.