Scale deposition is a difficulty encountered with water containing ions of sparingly soluble salts. A widely used technique for controlling scale deposition is by dosage of an antiscalant. Large quantities of polymeric scale inhibitors are used for scale control in cooling water systems, water desalination processes, and oil field operations. Like most conventional polymers, scale inhibitors are built for long existence and persist for many years after their disposal. Increasing environmental concern and discharge limitations have caused scale-inhibitor chemistry to move toward "green antiscalants" that readily biodegrade, have low mobility for minimum environmental impact, and are cost-effective. This review summarizes efforts to develop cost-effective ecologically benign scale inhibitors. Currently, the most promising green scale inhibitors are based on poly(aspartic acid). However, field operation data are very limited, and widespread use of poly(aspartic acid) scale inhibitors awaits field operation experience.