Czochralski‐grown dislocation free silicon crystals containing approximately 7.5, 9.9, and 18×1017cm−3oxygen atoms have been annealed at 750, 1050, and 1200 °C for times varying between 20 and 216 h. Neutron transmission spectra measured at reflection 111 in backscattering geometry reveal mean lattice contractions of the order of 5×10−5and lattice parameter fluctuations up to &Dgr;d/d≊5×10−4. The measuring time for one spectrum is 15 min and an on‐line characterization of the defects produced during annealing is feasible. A combination of this technique with neutron small angle scattering, &ggr;‐ray diffractometry, and diffraction experiments with high‐energy synchrotron radiation opens new possibilities for investigations of oxygen precipitation in silicon crystals as used in very‐large‐scale integration semiconductor device technology.