One hundred and eleven patients with rheumatoid arthritis (RA) and 44 with progressive systemic sclerosis (PSS) were prospectively evaluated for evidence of Sjögren's syndrome (Ss). The diagnosis was established when a patient with a lip biopsy focal lymphocytic infiltration score of greater than or equal to 2+ in Tarpley's scale had keratoconjunctivitis sicca (KCS) and/or xerostomia. Out of 44 RA and 10 PSS patients with positive lip biopsy, 34 and 9 had criteria for Ss respectively, suggesting a 31% prevalence of Ss in RA and a 20.5% in PSS. Six per cent of the RA patients spontaneously offered complaints of subjective xerophthalmia whereas 11.1% and 22.2% of those with PSS did so for subjective xerophthalmia and xerostomia respectively. However, specific questionnaire elicited subjective xerophthalmia in 38.2% and subjective xerostomia in 5.9% of the RA patients, whereas in 55.5% and 66.7% of the PSS ones respectively. Parotid gland enlargement was detected in 20.6% of the RA and in 44.4% of the PSS patients with Ss. Anti-Ro (SSA) antibodies were present in the sera of 23.5% and 33.3% of them respectively. Severe extraglandular manifestations were unusual in both groups. Our results suggest that, although both Ss in RA and that in PSS lack prominent exocrine gland symptomatology, certain differences between the two and similarities of the latter to primary Ss, would not justify the term 'secondary Ss' for the syndrome accompanying scleroderma, as it has been applied to that accompanying RA.