An apparatus which has been used to study the (p, 2p) reaction at 387 MeV is described. Two magnetic spectrometers analysed the momenta of the two outgoing protons in the range 440 MeV/c to 780 MeV/c and with a 10° angular range in the scattering plane. The resolution of the system was limited by multiple scattering in the acoustic spark chambers which were used to locate the particle tracks through the spectrometers. © 1969.