Sjögren's syndrome is a common accompaniment of rheumatoid arthritis and other connective-tissue diseases as well as several diseases thought to have an immunological basis. Despite the wide spectrum of clinical features and serological abnormalities the condition is, if anything, underdiagnosed. A clinical subgroup of patients with Sjögren's syndrome can be distinguished by their pronounced hypergammaglobulinaemia, widespread and prominent immunological abnormalities, severe salivary gland swelling, and mild or absent arthritis. It is in this group that lymphoma development has been a complication.