A rotational acceleration impulse to a head, as occurs at traffic accidents, sport injuries, assaults and falls, induces a diffuse brain damage that eventually could result in persistent neuropsychiatric deficits and neurodegeneration. Emphasis has been concentrated on the relative motion of the brain inside the skull during head impact, whereas less attention has been paid to whether intracranial pressure changes are generated and, if so, the implications thereof. In the present experimental study we investigated in an animal model system, based on rabbits, if a sagittal, anterior-posterior rotational acceleration of a head generated intracranial pressure changes, recorded by fibre optic pressure sensors, inserted ipsilaterally in the parieto-temporal and the occipital lobes. Two levels of rotational acceleration were used in the experiments; one higher, corresponding to the threshold limit for moderate diffuse brain injury, and one lower, close to being noninjurious. Several pressure recordings were performed in each rabbit at the two acceleration levels. The pressure recordings invariably revealed the same general characteristics of rapid, positive and negative pressures within the brain, with variations in amplitude and duration, lasting for up to 10 ms. A major finding was the generation of powerful negative pressures, as low as 0.3 bars in absolute pressure. The most prominent difference in amplitudes of the negative peak pressures between the two applied acceleration levels was demonstrated at the parieto-temporal location. The presented pressure recordings are the first to disclose the generation of transient, powerful intracerebral pressures at rotational acceleration of the head, which must be considered in studies of brain injury generation and distribution as well as prevention.