The relationship between root caries, oral sugar clearance, salivary flow rate, and salivary counts of mutans streptococci, lactobacilli and Candida has been studied in a group of 22 rheumatic patients (age range 40–72 years). The study group comprised all subjects volunteering for a clinical trial on relief of dry mouth symptoms. The median salivary flow was 0.09 ml/min at rest and 0.9 ml/ min during chewing stimulation. The median sugar clearance time was about 5 min in the sublingual area and 16 min in the lower buccal vestibule. For subjects with 0–2 root caries lesions the clearance time at both sites was shorter than for subjects with 3 or more lesions (p < 0.05). A long oral clearance time was significantly correlated with age, root caries (DS and DFS), low resting salivary flow, and high salivary counts of mutans streptococci. It is concluded that root caries in rheumatic patients with low salivary flow is significantly related to oral sugar clearance time.