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The interplay between superconductivity, magnetism and crystal struc-ture is a central issue in the study of the high Tc cuprates. The transition metal compound La2-xBaxCu04 (LBCO) was the very fir thigh Tc superconductor, discovered by J. G. Bednorz and K. A. Muller in 1986. However, it has been much less extensively studied than other high Tc materials, due to the diffi-culty of growing large single crystals. With our Image Furnace facility, we have successfully grown high quality, large LBCO crystals (with xrv0.095, 0.08, 0.05 and 0.025) on the underdoped side of the well known 1/8 (x=0.125) anomaly in this material 's phase diagram. Using our rotating anode X-ray source at McMaster University we have performed high-resolution X-ray diffraction studies on our x=0.095 and 0.08 samples and on a 1 / 8 doped LBCO (x=0.125) crystal grown by our collabora-tors. The X-ray study mapped out a sequence of tetragonal and orthorhombic crystal structures with temperature, which were known from earlier measure