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BACKGROUND Identification of atrial tachycardia (AT) mechanism remains challenging. OBJECTIVE We sought to investigate the added value of entrainment manoeuvres (EM) when using new high-density activation mapping (HDAM) technologies for the identification of complex left atrial tachycardias (AT). METHODS Thirty-six consecutive complex ATs occurring after ablation of persistent AF were prospectively analysed. The AT mechanism was diagnosed in two steps by two experts: 1) based on HDAM only (Coherent, CARTO Biosense Webster) and 2) with additional analysis from EM. RESULTS EM resulted in AF in one patient, which was excluded from the analysis. Ten of 11 single loop macro-reentry identified by HDAM were confirmed by EM. Only 4 of the 14 double loop macro-reentries identified by HDAM were confirmed by EM (in 10 patients, EM unmasked a passive activation of one of the visual circuits). One sole micro-reentry circuit identified by HDAM was confirmed by EM. A combination of macro- and micro-reentry circuits was visualized in three ATs using HDAM. However, EM revealed a passive activation of the visual macro-reentrant loop in 2 of these 3 cases. By using HDAM in 6 out of 35 ATs (17%), no univocal mechanism could be identified whereas EM finally enabled the diagnosis of five micro-reentry circuits and one macro-reentrant AT. All of the diagnoses made from EM on top of HDAM were confirmed by ablation. CONCLUSION Entrainment manoeuvres are still useful during mapping of complex left atrial tachycardia, mostly to differentiate active from passive macro-reentrant loops and to demonstrate micro-reentry circuits.