Plaque and gingival bleeding were scored and probing, radiography, and histologic methods were used to evaluate clinical methods for estimating alterations of supporting structures at functioning endosseous dental implants. Twelve implant abutment posts in three Labrador retriever dogs were assessed. The observation period was 3 months of submerged healing followed by 6 months in function. In the presence of daily gingival cleaning, both plaque and gingival bleeding scores were reduced on implant abutments. No correlation was found between gingival scores and the degree of bone resorption. The correlation between probing and radiographic measurements was studied by comparing 136 parallel measurements. The average difference was 0.4 mm. Discrepancies were observed when evaluating bone loss that reached the shoulder area. Better accordance was obtained when moderate (2 to 4 mm) or extensive (6 to 8 mm) resorption was assessed. Histologic evaluation indicated alternating regions of implant-bone contact and fibrous encapsulation. Progressive infiltrates were observed in the permucosal area, sometimes extending into the deeper parts of the supporting bone. A combination of probing and radiographic measurements seems to give the most reliable information about the level of bone support and is recommended to be included in routine control of implant abutments.