This report provides information on quantities of pesticides used by U.S. farmers in 1966, and comparisons with similar 1964 data. Pesticides included are insecticides, herbicides, fungicides, miticides, rodenticides, fumigants, growth regulators, and defoliants and desiccants. Information is presented on leading products such as DDT, toxaphene, and 2,4-D. Approximately 90 different products or groups of products are included. The study is based on a survey of about 9,600 farmers throughout the 48 contiguous States. Survey data were expanded to represent regional and U.S. pesticide usage for selected crop, livestock, and other purposes. Findings show that farmers used just over 350 million pounds of pesticides in 1966 (exclusive of sulfur and petroleum). This was a 10-percent increase over 1964. Farm pesticides in 1966 including sulfur and petroleum were valued at $561 million in that year. Crops accounted for over 90 percent of all pesticides used by farmers in 1966. Insecticides were the major pesticide products, with farm use amounting to 149 million pounds. Ninety-two percent of the insecticides were used on crops and nearly half of these, on cotton. Farmers used 115 million pounds of herbicides in 1966, up 37 percent over 1964. Corn was the major recipient of herbicide products, accounting for over 40 percent of those used on crops. Farm use of fungicides and fumigants each amounted to 30 million pounds in 1966.