Celtic glasses of different colors, opaque or transparent, in the form of beautiful ornaments were characterized according to elemental composition by energy-dispersive x-ray fluorescent analysis. This analytical technique is nearly non-destructive and was the method of choice for this project. The Celtic glasses were loaned for the time of analysis by museums and private collections under the guarantee that no harm would be done to the objects. The main goal was to establish a reliable analytical method to achieve qualitative and quantitative results within acceptable errors. The historical and physical background is given and describes the motivation for this task. Preliminary tests carried out before the series measurements started are described and show that within a certain error range good results can be expected from samples of different shapes, with uneven or rough surfaces. Experimental conditions for the determination of light elements and subsequent extension to medium- and high-Z elements are described. The results from the test studies and for selected samples with various colors and shapes are presented.