Abstract　 　 
Accreting millisecond X-ray pulsars (AMXP) are a subclass of low-mass X-ray binary transients that host an old, weakly magnetic neutron star that accretes mass from a companion star and has been spun up to millisecond periods via transfer of angular momentum. Since they have been spun up by accretion, their initial mass should have increased by at least 0.1-0.2 M_Sun compared to the canonical neutron star mass. AMXPs are therefore excellent systems for the search of massive neutron star and tightly constraining their equation of state (EOS). I will present the results of an extensive observational campaign aimed to estimate the masses of AMXP systems through dynamical measurements.