An experimental technique for measuring the feeding behavior of copepods on small time scales is important because grazer/micro-patch interactions in the ocean are probably short (minutes to hours). By placing copepods with empty guts into a known food concentration and monitoring the rate of increase in gut contents until defecation begins, usually 20 to 100 rain, the volume of water swept clear of particles per min can be calculated. This process is easily quantified by using phytoplankton as food and measuring the gut contents by fluorometry. The utility of this technique is demonstrated in the laboratory and at sea. contribute to this variation; copepods with feeding appendages working continuously in a patchy food environment would ingest different amounts of food per unit time. Alternatively, variation in the level of gut fullness could be due, in part, to changes in feeding behavior. The relative contribution of these two factors (i.e. feeding behavior and food patchiness) to the observed changes in gut fullness cannot be separated in a field study without a precise description of the food environment as well as an improvement in understanding of the short-term feeding behavior of the grazing copepods. This paper describes a simple method for measuring the feeding rate of herbivorous copepods over short periods.