The objective of the present study was to compare the reliability of four partial-mouth protocols for assessing shallow, moderate, and deep sites for periodontal pocket depth and clinical attachment levels. Periodontal pocket depth and clinical attachment level measurements were recorded for 156 subjects (age > or = 30). The four models of partial-mouth protocols compared were: Model I: all sites per tooth in the random half-mouth protocol randomly selecting one maxillary and mandibular quadrant, Model II: buccal sites in a full-mouth protocol, Model III: buccal sites in the random half-mouth protocol randomly selecting one maxillary and mandibular quadrant, Model IV: all sites per tooth using Community Periodontal Index teeth. In comparison with full mouth examination, Model I did not show significant differences for periodontal pocket depth and clinical attachment level parameters. Models II and III were different for some periodontal pocket depth means, and Model IV significantly overestimated all clinical parameters related to periodontal disease. Model I appears to be adequate to substitute for the full-mouth examination to assess the prevalence and severity of chronic periodontal disease in adults.