Based on the monetary value withdrawn from firms in the extortion process, this study estimated the cost to businesses of mafia extortion at one billion euros, corresponding to just over 1.4 percent of the 2006 gross regional product of Sicily. The average monthly payment is approximately 600 euros per business. The findings support the hypothesis that in most cases, the pervasive involvement of the mafia in the extortion of Sicilian businesses constrains business growth. In absolute terms, the sector for which criminal extortion is the most costly are construction and commerce (mostly retail). For diffusion and territorial density, these businesses form the productive system of Sicily. The evidence matches judicial proceedings that show the mafia operates under the philosophy of charging little to any one business, but charges all businesses, which ensures the expense is tolerable for a business while maximizing profit for the mafia. This analysis did not attempt to estimate the benefits businesses may receive from the mafia for the extortion money paid. The primary benefit consists of ensuring the business’s survival. Secondary benefits may include protection against the risks of being cheated in business transactions, assistance in disposing of competitors, and attracting customers. 2 figures, 4 tables, and 44 notes