Prostaglandin E2 (PGE2) and alkaline phosphatase (ALP) have often been measured in gingival crevicular fluid (GCF) as possible indicators of gingival inflammation and bone metabolism. Osteocalcin (OC), a major component of bone matrix, is mainly produced by osteoblasts, and could also be considered as a marker of bone turnover. The aims of this preliminary study were to examine if OC was present in GCF and to assess the relationships of OC, PGE2 and ALP in GCF to periodontal conditions. GCF samples were collected with durapore strips from 34 healthy, 72 gingivitis and 118 periodontitis sites in 17 subjects. ELISA techniques were used for the determinations of OC and PGE2. ALP was measured spectrophotometrically by using p-nitrophenyl phosphate as substrate. Total amounts and concentrations of PGE2 and ALP were significantly higher in periodontitis as compared to healthy and gingivitis sites, and were significantly and positively correlated with probing depth (PD) and gingival index (GI). OC was present in GCF from both healthy and diseased sites with mean concentrations more than ten times greater than normal serum levels. Total OC amounts from strips soaked with GCF from periodontitis sites were significantly higher than those found in healthy and gingivitis sites. When the data were expressed as concentrations, OC showed significantly positive correlations with GI, but not with PD. However, total amounts of OC significantly correlated with both clinical parameters. OC, PGE2 and ALP were found to have significantly positive correlations with each other, both when expressed as total amounts and concentrations. These data suggest that a significant amount of OC present in GCF is produced locally by periodontal tissues.(ABSTRACT TRUNCATED AT 250 WORDS)