Numerous reports have suggested a relationship between marginal adaptation of dental castings and periodontal tissue health, and this study examined this relationship quantitatively. Forty-two crown restorations in 29 randomly selected patients were selected for this study using three criteria. (1) The crowns were placed at the University of North Carolina School of Dentistry; (2) the crowns were in service for a minimum of 4 years; and (3) the crown margins were within the intracrevicular crevice (subgingival). Replica impressions of the facial margins of specific crowns were made with a vinyl polysiloxane impression material, and poured casts were prepared for scanning electron micrograph evaluation. Marginal discrepancy measurements were identified on each micrograph at 10 equally spaced locations along the margin and averaged for each specimen. Periodontal indices of pocket depths, crevicular fluid volume, and gingival index were accumulated for clinical measurements. Pearson correlation and Bonferroni adjusted probability tests were performed, but no significant correlation was found between marginal discrepancy (0.16 +/- 0.13 mm) and pocket depth (2.4 +/- 0.9 mm). However, a strong correlation (p less than 0.001) existed between marginal discrepancy and gingival index (2 +/- 0.8) and between marginal discrepancies and crevicular fluid volume (49.9 +/- 31.1). These results established that a significant quantitative relationship existed between the marginal discrepancy and periodontal tissue inflammation for subgingivally located crown margins.