Seven patients were evaluated at a mean duration of 8.4 yr after sustaining inhalational injury associated with burns. At the time of re-examination, the patients were asymptomatic and had normal chest X-rays, and arterial blood gases. Three of the seven patients had abnormally elevated serum calcitonin levels. The spirometry (FEV1) measurements showed an inverse trend to that of the serum calcitonin levels. The elevated calcitonin levels had an abnormal predominance of the procalcitonin component as assessed by several region specific antisera. The serum calcitonin also showed a significant correlation with the hormone level which had been obtained at the time of prior discharge from the hospital (r = 0.91). Although there appears to be no or minimal chronic pulmonary sequela to inhalational injury in burns by pulmonary testing, we speculate that the hyperprocalcitonemia in some of the patients may reflect a long-term hyperplastic response of the bronchio-epithelial pulmonary neuroendocrine cells. The potential significance of this and other lung-associated endocrine markers is discussed.