The frequency and percentage of enteric rods, staphylococci and Candida were determined in 973 subgingival samples collected from 535 patients subjected to different periodontal treatment procedures. The analysis was performed with culture technique using selective and nonselective media. One or more organisms were detected in 65.5% of the samples and in 76.7% of the patients. In most samples enteric rods, staphylococci and/or Candida constituted a small amount of the total microbial viable count. Enteric rods exceeded 10% of the total viable count in 30 samples. Staphylococci occurred in more than 10% in only 3 samples. In these 3 samples, enterics constituted more than 10% of the total viable count. Candida was not found to exceed 10% of the total viable count in any of the samples. No statistically significant correlation was found between the presence of any of the target microorganisms and kind of periodontal treatment procedure received, antibiotic administration or sample transport time.