A rapid increase in cases of shrimp diseases has accompanied the expansion and intensification of penaeid shrimp culture throughout tropical and subtropical regions of the world. A wide variety of both infectious and noninfectious diseases involves different stages and species of shrimp, affecting the shrimp industry in diverse ways. Six of nine viruses known to infect penaeids have caused considerable financial loss to some facilities, and two of those, BP (Baculovirus penaei) and IHHNV (the probable picornavirus infectious hypodermal and hematopoietic necrosis virus), have created a significant barrier to development of the industry in North America. Diseases caused by other agents such as bacteria, fungi, and protozoans have also impacted shrimp production, and each disease has been dealt with differently. A compelling need to halt the spread of some of these and other agents into uncontaminated geographic areas exists, especially during this relatively early period of shrimp aquaculture. On occasion, impacted production has been attributed also to poor water quality, toxins, malnutrition, and other noninfectious causes. Not all adverse infections and conditions harm the hosts. A few infectious agents such as peritrichs that attach externally to the cuticle when high organic levels occurred in the system serve as biological indicators. If neither infesting larvae nor occurring during periods of low dissolved oxygen concentration, none of several of these ciliate protozoan species has been reported to cause mortalities. Other agents apparently cause little or no disease to the shrimp, but they can influence human health. For example, the bacteria Mycobacterium marinum and Vibrio parahaemolyticus have caused chronic granulomatous lesions on the hands of shrimp-handlers and gastroenteritis in those who ate the product, respectively. Those who eat inadequately prepared products can acquire potentially harmful infections with microphallid trematodes and at least one juvenile nematode, Hysterothylacium, type MB. Other agents that usually have little influence on shrimp health can influence greatly the market value of the product. As examples, several bacteria have caused shell-disease, resulting in dark obvious lesions in the exoskeleton, and bopyrid isopods infesting the branchial chamber have caused a large unsightly protrusion of the cephalothorax. This study was conducted in cooperation with U.S. Department of Agriculture Grant No. 85-CRSR-2-2538 and U.S. Department of Commerce, NOAA, NMFS, PL99-659, Project No. 2-lJ-3.