Connective tissue disorders (CTD) have a relatively high incidence of pulmonary complications but their delineation has been hampered by difficulties inherent in the diagnostic techniques. One fresh approach to this problem is based on a clustering method that uses data from 8 separate investigations to cluster the patients into 4 distinctly separate categories representing normal nonsmoker, normal smokers, those with active interstitial lung disease and those with bronchiolitis. Using this method, a large group of patients with CTD have been examined to assess the nature and extent of their pulmonary complications. Subjects in the first cluster had a normal test profile across all variables, and included no current active smokers. The normal smoking cluster contained only smokers who had a high total lavage cell number with a relative increase in macrophages and a decrease in lymphocytes. In this group, all respiratory variables were normal with the exception of a mildly depressed DLCO, also known to be associated with smoking. The general characteristics of the active interstitial lung disease cluster was a markedly depressed DLCO indicating impaired gas exchange, and elevated gallium index, bronchoalveolar lavage (BAL) cell number and neutrophil and lymphocyte percentages, all indicating an active inflammatory process. However more careful analysis of this group suggested the presence of 2 subgroups, one with a lymphocytic alveolitis, and another with a neutrophilic alveolitis. The bronchiolitis cluster characteristics were a markedly depressed maximal mid expiratory flow rate and raised BAL lymphocyte percentage and gallium index. The distribution of patients within the cluster groupings suggested that Sjögren's syndrome, often an accompaniment of other CTD, is most frequently associated with pulmonary disease.(ABSTRACT TRUNCATED AT 250 WORDS)