In order to appraise the significance of respiratory abnormalities in primary and secondary Sjogren's syndrome (pSS and sSS), we evaluated 40 patients with pSS, 26 with sSS, 40 with rheumatoid arthritis (RA) but no SS, and 100 age- and sex-matched control subjects. The most common functional abnormality was diffuse interstitial lung disease (DILD) in patients with pSS (37.5 percent) and obstructive ventilatory defect in RA and sSS patients (40 and 19 percent, respectively). DILD was also present in the last two groups (11.8 percent in sSS and 27.5 percent in RA), while obstructive defect was rare in pSS (2.5 percent). Abnormalities suggesting small airways disease were present in all patient groups and also in the control group with similar frequency. Patients with extraglandular pSS had most often DILD (52 percent). Patients with pSS and cryoglobulinemia had low C3 and C4 levels and decreased Dco, suggesting that interstitial lung disease may be a result of immune complex deposition. Clinical input of the functional abnormalities was minimal, expressed as dry cough and mild dyspnea. Pneumonia was not frequent, while pleurisy was present only in patients with sSS and RA. We suggest that, even though pulmonary abnormalities can frequently be detected with sensitive tests in patients with SS, they are not significant if compared with control subjects and are clinically negligible.