Previous investigations have shown that crevicular fluid iron concentration (CFIC) is higher in periodontally diseased sites. The present study was conducted to determine whether periodontal treatment changes the CFIC to levels found in healthy sites in the same persons. To test the significance of iron content in gingival fluid as an indicator of periodontal disease severity or activity, CFIC was determined for healthy sites and diseased sites treated with scaling and root planing alone or in conjunction with surgery both before and after treatment. CFIC was increased in diseased sites, but the iron concentration in crevicular fluid was not a good indicator of changes in disease severity resulting from periodontal treatment. Treatments produced an increase in the CFIC that may be more related to the status of the microcirculation than to the disease process itself.