Four glass-ionomer cements were examined for solubility by measuring the fluoride release from a simulated dental restoration. From this study it may be concluded: 1. Glass-ionomer cements as luting agents for dental prostheses release significant quantities of fluoride. 2. Commercially available cements vary in the amounts of fluoride released. 3. The cements with lower powder-to-liquid ratios demonstrated greater fluoride release. 4. The significant release of fluoride indicated that glass-ionomer cements could be effective in reducing caries.