The disorder-order phase transitions in Cu-Al-Be shape memory alloys were studied by in-situ X-ray diffraction. Isothermal measurements in an inert gas chamber were made on ribbons of Cu-Al-Be alloys, obtained by melt spinning. A position sensitive detector was used for a fast record of the X-ray signal on a theta-theta geometry diffractometer. Each ribbon was used as the heating element, avoiding the need of a heating sample holder and obtaining a better measurement of the temperature with a thermocouple attached directly to the ribbon. The order transition was followed at different temperatures after a high temperature annealing (700 degrees C) in the disordered beta-phase region. A first order transition was observed from disordered beta (A2) to ordered beta(1) (DO3), without prior beta (B2) ordering. No precipitation was detected during this fast measuring procedure.