The number of decayed, missed and filled permanent teeth (DMFT), the degree of periodontal inflammation (Periodontal Status Index, PSI), stimulated salivary flow rate and the concentrations of total protein, lactoferrin, lysozyme, myeloperoxidase, salivary peroxidase, calcium, potassium, sodium and thiocyanate in whole saliva of 26 adult asthma patients were compared with those of 33 non-asthmatic controls. The saliva was also analysed for mutans streptococci, lactobacilli, total anaerobic flora and Candida spp. The mean PSI (p < 0.05; 95% confidence interval for the difference between means (95% CI) 2.47-25.30) was higher and the mean stimulated salivary flow rate (p < or = 0.05; 95% CI 0.57-0.55) was lower in the asthmatic group than in the control group. No differences were found between the groups in non-immune defense factors, except for myeloperoxidase. The myeloperoxidase concentrations were higher in asthmatics than in non-asthmatics (p < 0.05; 95% CI 4.4-134.0 ng/ml). No differences in microbial counts were found. It was concluded that stimulated salivary flow rates decrease while myeloperoxidase concentrations increase in adult asthmatic patients compared with non-asthmatic adults. The higher concentrations of myeloperoxidase are explained by a higher PSI in asthmatics.