Elastase-alpha 1 proteinase inhibitor (E alpha 1PI) concentrations were assessed in gingival crevicular fluids and evaluated in relation to the clinical signs of periodontal disease. 7 gingivitis patients (group G), 38 patients with adult periodontitis and clinically stable lesions (group AP), 21 patients with rapidly progressive periodontitis and clinically stable lesions (group RPP) and 11 patients with either adult periodontitis or rapidly progressive periodontitis and clinically progressive lesions (group Pr) were studied. 6 healthy subjects served as the control group (group H). Significantly differences were observed in the E alpha 1PI concentration between the healthy, gingivitis, clinically stable periodontitis and clinically progressive periodontitis group. In the control group, no E alpha 1PI was detected. Groups G, AP and RPP showed mean E alpha 1PI concentrations of 10.95 +/- 4.96 micrograms/ml, 35.55 +/- 18.64 micrograms/ml and 38.56 +/- 20.89 micrograms/ml, respectively. In these groups, high enzyme levels were correlated with clinical signs of inflammation. The highest E alpha 1PI levels were observed in the clinically progressive lesions. However, they were not necessarily associated with bleeding on probing or clinical evidence of inflammation. These data suggest that a significant increase in crevicular E alpha 1PI levels may be an early manifestation of a progressive or potentially progressive periodontal lesion.