The corrosion of different stainless steels in high temperature and high pressure urea environment has been analyzed by means of autoclave immersion tests to investigate the corrosion mechanism in each case. These experiments have been designed to reproduce the very corrosive conditions of urea strippers, which operate at 140-200 bar and 180-210ºC. A high Cr-high Ni-Mo austenitic stainless steel commonly used in urea equipment, UNS S31050, and several duplex-type stainless steels, UNS S31803, UNS S32750, UNS S32760 and TUBACEX UREMIUM29 (UNS S32906) have been involved in this study. Results have shown that UNS S31050 experiences active corrosion due to the absence of oxygen in the experimental setup, whereas TUBACEX UREMIUM29, a superduplex stainless steel specially developed for urea plants, remains passive and with the lowest corrosion rate.