Patients with immune system abnormalities were pair‐matched to immunocompetent clinic patients by age and Plaque Index. Clinical examination included comprehensive health histories with summaries of antibiotic experience, Plaque Index (P 1.I.), Gingival Index (G.I.), Periodontal Disease Index (P.D.I.), caries experience (DMF‐T) and full mouth radiographic surveys. Efficiency of matching was confirmed as tests of significance between sample means for age (11.3, 11.3) and P1.I. (1.33, 1.34) showed no difference between the immunodeficient and clinic patient groups respectively. No clinical or radiographic evidence of attachment loss was noted in either group. A significant and consistent diference was observed in gingival inflammation and caries experience. The G.I. was lower (x̄=1.05) in immunodeficient patients than that recorded in clinic patients (x̄=1.46) in all pairs. Similar results were observed for caries experience, and 8 immunodeficient patients demonstrated DMF‐T scores