Twelve patients are described with features of cryptogenic fibrosing alveolitis (CFA) with associated florid digital vasculitis (DV). Nine patients had features of various 'connective tissue disorders' involving systems other than the lung, but three had no such features. The immunological features of these patients with DV have been compared with a group of 17 patients who had CFA alone ('lone CFA') and in whom the same range of special laboratory tests were being undertaken concurrently. The group with DV had a higher erythrocyte sedimentation rate and a higher serum IgM, but the most interesting immunological distinction was an increased prevalence of antinuclear antibodies with a nucleolar staining pattern. In addition, the group with DV also had a greater prevalence of single stranded DNA antibodies and of smooth muscle autoantibodies. Circulating immune complexes were not detected more frequently in the group with vasculitis. Ten of the 12 patients were initially treated with corticosteroids and neither the vasculitis nor the lungs improved. In eight the incapacitating DV responded to immunosuppressants (four) or penicillamine (four). In three of these eight patients the lungs also improved.