cyst vanishing or observation of a linear echoic scare (vestiges).The percentage of the solidified area was determined by Computer Assisted Design (CAD) program. The cyst inactivity was defined if the cyst content solidification was total or almost total (> 90%). RESULTS:The final evaluation of the 62 cysts showed a therapeutic efficacy of 87.1% (54 cysts), from which 48 (77.4%) reached a solidified pattern greater than 90% and six (9.7%) vanished. From the remaining nine cysts, three (4.8%) were referred to surgery in the second and third evaluations due to no alteration of its pattern (all cysts type 2); two (3.2%) reached solidification lower than 90%; and three (4.8%) relapsed (cysts type 2). No major complications or mortality were observed, neither secondary echinococcosis after PAIR. CONCLUSION: PAIR is an effective and safe method to treat cysts type 1 and 3a of the WHO-IWGE US classification. The efficacy was 96.2% in cysts type 1 and 95.8% in cysts type 3a. It is not indicated in multivesicular cysts (type 2), in which the therapeutic failure was 50%.