Fifty-six patients with kryptogenic fibrosing alveolitis were followed up during 6.3 years (from 1.5 to 19.3 years) after their first functional examination including cardiac catheterization. Twenty-two out of 56 patients died during the follow-up. The significance of individual functional tests as predictors of the survival was evaluated by means of actuarial survival probability curves. Four variables were predictive for nonsurvival: a mean pulmonary arterial pressure exceeding 30 mmHg, a vital capacity of 60% of the predicted value or lower, a CO diffusing capacity at rest less than 40% of the predicted value, an age at first symptoms over 30 years. Other variables were not significantly predictive for a given time of follow-up. A simple prognostic score derived from predictive variables was able to separate the subgroup of patients with unfavourable short-term prognosis. Among significantly predictive variables, a resting pulmonary arterial pressure over 30 mmHg appears to be the most important.