In 1971, U.S. farmers would have incurred additional costs of over $1.84 million if farm uses of the insecticide chlordane had been discontinued. Based on estimates of 1971 acreage treated with chlordane, this aggregate loss would have included $1.56 million in additional costs for alternative insecticides and $0.28 million in yield losses. Added costs for alternative insecticides would have ranged from $0.18 an acre for cotton to $6.77 an acre for corn. For producers of potatoes, tomatoes, strawberries, and certain vegetables, the added cost would have averaged about $2.25 an acre. Because alternative insecticides are not as effective as chlordane in controlling insects on citrus, strawberries, and certain vegetables, per acre yield losses for these crops would have been $31, $75, and $23, respectively. Total use of chlordane would have decreased by 601,000 pounds if farm use had been discontinued. But the increase in alternative insecticides would have been about 1.1 million pounds--primarily carbaryl and diazinon for com production and small amounts of phorate, EPN, parathion, and methyl parathion for other crops.