Plate samplers constructed of VB-inch thick masonite were used in a bioassay study of water quality in the Black Warrior River near Tuscaloosa, Alabama. The samplers were placed in a fertilized pond and allowed to accumulate a dense population of larval chironomids (Chironomidae) for one month. The samplers were then placed into the river at stations above the outfall of the uppermost industry and below each outfall of four industries. Counts of chironomids on each of the samplers were made after one week and comp.arisons were made between the average number of organisms on the samplers at stations above the outfalls and the average number at each of the stations downstream from the outfalls. It appeared that this inexpensive technique of bioassay can be useful in determining the effects of pollution on chironomids. Today there are more people with more leisure time demanding more clean freshwater for recreation than ever before. There is also an increased demand for more complex industrial goods and, subsequently, more complex waste products are being discharged into our streams and lakes. There exist a great need for rapid and efficient bioassay techniques to determine the effects of these pollutants on the fish and fish food organisms living in the receiving waters. Hester and Dendy (1962) described a multiple plate sampler constructed of 1/8-inch thick tempered hardboard ("masonite") and its use to determine the abundance of macroinvertebrate organisms in streams. The samplers were placed into streams tor periods of from 253 one to three weeks and then examined to determine the aquatic organisms that had accumulatd on the plates of the sampler. Dr. J. S. Dendy described a bioassay technique used to determine the effects of polluted water on larval chironomids (Chironomidae). The samplers were constructed of two 1/8-inch thick plates (3 inches square) of masonite separated by a 1-inch square plate of the same thickness. The plates were bound together with a nylon rope. Samplers were placed in a fertilized pond, allowed to collect a population of larval chironomids, and then placed into a polluted portion of a stream. Samplers placed into an unpolluted tributary stream served as controls. The plates were removed after three days and examined to determine the number of chironomids on the plates. After reviewing the results of the technique used by Dendy, this author initiated a study to determine the effects of industrial pollution on the fish and fish food organisms in a portion of the Black Warrior River near Tuscaloosa, Alabama. Chironomids are abundant in non-polluted waters of Alabama and are important food items in the diets of many forage fishes (Howell, et al., 1941).