Patent foramen ovale (PFO) closure is indicated in some cases to protect patients against embolic events. The aim of this study was to certify that the method of PFO closure to prevent microemboli (MES) is reliable, using contrast enhanced transcranial Doppler (cTCD) as a diagnostic and follow-up tool. METHODS: cTCD was performed before and after PFO closure in 20 patients. Results obtained a minimum of 12 months after the procedure were analyzed in this study. RESULTS: After the procedure, 14 patients (82%) showed no microemboli in cTCD at rest, but after provocative Valsalva maneuver (VM) microembolic phenomenon were still detected in 14 (70%): 7 (35%) <10 MES, 3 (15%) 10-20 MES and 4 (20%) had more than 20 MES ("curtain"). Only six of the total patients presented no MES in both resting and VM. CONCLUSION: These results showed a large percentage of patients with MES detection in a bubble study with transcranial Doppler more than one year after the procedure of PFO closure, showing right-to-left residual shunting. Despite the small number of patients, this study provides important data about this therapeutic decision.