The technique of peri-hypophyseal phlebography is briefly described and the theoretical bases that inspire its utilizations and indications are pointed out. On the basis of 20 preliminary cases, the main applications of this investigation are illustrated, with a particular attention concerning the early diagnosis of lesions too small or too dishomogeneous to be detected with certainly on CT (i.e. intrapituitary microadenomas smaller than 5 mm; associated intrasellar lesions as empty sella + pituitary tumor).