... The earliest X--ray observations were carried out in the mid--1970s. X--ray luminosities of order L erg/sec were detected in the 2-11 keV range in the direction of the Orion star forming region. ... These observations showed that the O and B stars were the brightest X--ray sources, and that TTs were also associated with emission. Feigelson and Kriss (1981) showed that some of the X--ray sources were associated with PMS stars which had not been previously detected which H surveys. ...