Operative conservatism, including delayed operative intervention, is recommended to promote tooth longevity. Effective conservative operative strategies for the permanent dentition are the occlusal preventive resin and the proximal only restoration. Conservative strategies for the primary dentition have proves less successful. Conventional and conservative restorations are vulnerable to caries recurrence, material failure, and technical deficiencies. Successful conservatism demands discerning diagnostic decisions, effective disease management, and technical excellence. The diagnostic accuracy of radiographs and visual criteria is briefly reviewed for proximal and occlusal caries. Improved visual ranking criteria are supported for occlusal caries diagnosis. The use of dyes for occlusal diagnosis is not recommended.