Diaphragmatic elevation or paralysis after open-heart surgery was retrospectively analyzed in 370 consecutive operations performed on 365 adult patients. The incidence of the complication was 7.2%. It was significantly correlated with ipsilateral pleural effusion and lower-lobe atelectasis, but no predisposing or causal factors could be identified. Diaphragmatic elevation did not prolong the hospital stay. Actuarial analysis of data from follow-up chest radiograms showed normalization of the diaphragmatic position within 6 months in 44% and within a year in 90% of the patients.