The low mass X-ray binary X1822-371 is one of the brightest LMXBs in the optical and it is also the prototypical accretion disc corona source. In spite of it has been widely studied, reliable constraints to the stellar masses have only been set in the last 5 years thanks to the detection of 0.59s X-ray pulses and fluorescent emission lines arising from the companion at Kem 300 km/s. Since the emission site of these lines is not the center of mass of the donor, a K-correction to Kem needs to be applied. We have computed the K-correction for X1822-371 which combined with other previous constraints to the system parameters yields Mns˜1.6. This result strongly suggests the presence of a massive neutron star in this system. Here we also present the results of a VLT+UVES high spectral resolution campaing in which we refine our previous work and set tighter constraints to the mass of the neutron star in this LMXB.