The past decade has witnessed an extremely rapid development in the "science" of mariculture, especially the design and operation of modern oyster seed hatcheries. The Department of Marine Culture at the Virginia Institute of Marine Science over the past seven years has developed an oyster hatchery system through research and cooperative efforts with the fisheries industry. This system, including the biological protocol to be described in detail on the following pages, has been tested successfully and is a modification of that system used at Chesapeake Sea Farms, Inc. in Ridge, Maryland. It is important to stress this system represents a totally integrated concept-an interdependent system, which, if taken apart and used as separate steps, will yield poor results, especially when modifying the oyster larval food diet. The detailed instructions are not meant to bore the expert, but are included to make sure the results can be reproduced.