The status quo of the research on Bloch oscillations in semiconductor superlattices is outlined. Bloch oscillations excited by femtosecond laser pulses have been investigated by different optical techniques. They have allowed measurement of the internal electric field changes associated with the charge oscillations, the emitted terahertz electromagnetic radiation and the nonlinear coherent optical response, all directly in the time domain. The main results are summarized and critically reviewed. The potential of Bloch oscillations for practical applications in terahertz radiation sources is assessed.