In contemporary fusion research beryllium (Be) plays an important role. It is being assessed as a suitable low Z material for plasma-facing walls, limiters and divertors. Several authors have already made detailed spectroscopic studies of Be in tokamak plasmas. In the present report a critical evaluation has been made of radiative transitions in neutral, singly and doubly ionized Be (Be I - Be III), with emphasis on the needs for diagnostic measurements in plasmas. In addition to an extensive literature survey we also report new experimental and theoretical results. The former were obtained by means of the beam-foil excitation technique, whereas the theoretical analyses were performed using the superposition of configurations (SOC) method of Cowan. On the basis of available theoretical and experimental data critically evaluated oscillator strengths and transition probabilities are presented for a number of transitions in Be I - Be III.