This study was designed to characterize histologically the gingival lesion associated with visual signs of inflammation and bleeding after probing. Sixty midfacial gingival sites in 26 persons were evaluated for visual presence of absence of inflammation and bleeding after probing using a controlled insertion pressure of 25 gm. In order to delineate the area for histologic analysis, a reference incision was made on the facial surface of the gingiva which corresponded to the depth and mesio-distal extent of the area probed and evaluated for signs of inflammation. Gingival biopsy specimens were morphometrically analyzed to determine the percentages of cell rich--collagen poor connective tissue and blood vessel lumens. Histometric data were grouped and compared with respect to the presence or absence of inflammation and bleeding. Specimens associated visually with inflammation had significantly greater percentages of both cell rich--collagen poor connective tissue and blood vessel lumens. Bleeding upon probing was associated with a significantly greater percentage of cell rich--collagen poor connective tissue without an increase of blood vessel lumens. It was concluded that both observed signs of inflammation and bleeding after probing can be used to detect inflammatory lesions in the gingiva. However, in areas inaccessible for evaluation of inflammation, bleeding determinations using controlled insertion pressures provided an objective diagnostic method for detecting the presence of an inflammatory lesion.