The aim of this study was to assess the sensitivity of contrast echocardiography in the diagnosis of permanent (atrial septal defects, ASD) and transient (patent foramen ovale, PFO) interatrial communications under basal conditions, after Valsalva manoeuvres and coughing. Sixty-four patients suspected of having defects of the interatrial septum were studied. The results of echocardiography were compared with those of cardiac catheterisation, the classical method of reference. The sensitivity of contrast echocardiography was significantly improved in the diagnosis of PFO by the cough test (100%) compared with contrast echocardiography during spontaneous respiration (55%). Similarly, the cough test increased the sensitivity of contrast echocardiography in the diagnosis of ASD (96% compared to 83%). The specificity was good in both cases, about 90%. The cough test was a better method (98%) than Valsalva manoeuvres (59%) for the potentiation of interatrial right-to-left shunts. The results of echocardiography and catheterisation explain the mechanism of the right-to-left shunt during spontaneous respiration, Valsalva manoeuvres and coughing. The passage of the microbubbles from the right to the left atrium occurs during early systole when the atrioventricular valves are closed. The right-to-left shunt is potentiated by provocative manoeuvres. The demonstration of a right-to-left shunt by contrast echocardiography therefore indicates the presence of an interatrial communication; our results show that this non-invasive technique is a reliable method of diagnosing ASD and PFO.