Worldwide, plant growth regulators (PGRs) account for only 3% to 4% of the total sales of plant protection agents. This limited market potential, the rising costs of development and registration, and the demand for high profitability have created major constraints to the introduction of new PGRs. Conversely, PGRs have become an integral part of agricultural and horticultural practices and one might assume that the market is sufficiently lucrative to those companies active in this area. In the past decade, at least seven new PGR products have been introduced. In many cases, reduced requirements for registration have lowered the financial risks relative to expected profits.