Free lysine, an amino acid produced industrially by microbial fermentation, is becoming increasingly important in intensive livestock production. Estimates are made of the economic impact of its wider use. The economic impact of doubling the current utilization rate of free lysine in pig production is also investigated. It is shown that the use of free lysine as a replacement for protein concentrates is marginally profitable at current utilization rates and prices. However, if experimental techniques of doubling free lysine utilization rates are adopted by the industry, the use of free lysine could lower costs of pig diets and substantially replace high lysine protein concentrates in pig diets.