An X-ray excited optical luminescence (XEOL) technique using laboratory soft X-rays and synchrotron radiation in the visible-UV and soft X-ray region will be discussed. It is shown that XEOL takes advantage of the penetration power of the X-rays and the tunability of the photons from a synchrotron source. Thus XEOL provides some sampling depth and site selectivity and allows for the probing of underlayers and buried interfaces. XEOL studies of porous silicon and a poly-vinyl-carbazole film will be used to illustrate that this technique is suited for the study of organic luminescent materials and organic electroluminescence devices (OELD).