Every year (by the end of the summer) a Call for Admission is issued, stating the number of available positions and grants (including grants from external research institutes, e.g. INFN, INAF, Progetto Lagrange, etc). Some of the grants may be reserved to foreign candidates.
The entrance test (which usually takes places in autumn) consists of two parts: a written examination on general physics (mechanics and termodynamics, electromagnetism, basic quantum mechanics) and an oral examination.
The list of candidates admitted to the Ph. D. program is based on this competition and the best candidates in the list receive the grant. Grants for foreign candidates are awarded on the basis of their curricula.