There is an annual tuition fee, currently in the amount of 2750 euros (for the academic year 2008/2009).
The Portuguese funding agency FCT holds annual competitions for doctoral fellowships which cover tuition fees and living expenses. More information can be found on the web page
http://www.fct.pt/apoios/bolsas/concursos/
For Brazilian citizen the program "Ciências sem Fronteira" might be interesting:
