The purpose of this study was to determine and to compare the titers of salivary anti-A and anti-B antibodies in two groups of patients with periodontal disease as measured by Russell's Periodontal Index (PI). Forty volunteer subjects, who were new patients assigned to a screening clinic, were selected for the study based on the following criteria: (1) blood group, (2) medical history, (3) age and (4) periodontal condition. One group of patients (N = 20) had a PI of less than 2.0 and the other group of patients (N = 20) had a PI of greater than 4.0. Following screening, a 10-ml sample of unstimulated whole saliva was collected, centrifuged and frozen. Within 30 days the saliva was thawed, titrated and tested for presence of anti-A and anti-B. Saliva agglutinin titers were determined using a variation of previous testing techniques. Statistically significant differences between the two groups were not obtained in the titers of salivary anti-A (U = 192.5; P greater than 0.1) or the titers of salivary anti-B (U = 162.8; P greater than 0.1). All 40 group O patients were found to have anti-A and anti-B in their saliva.