CSF pressure recordings have been taken from the lumbar region and the cisterna magna of 16 patients during coughing in the sitting position. Isolated coughs of low amplitude have been studied. The lumbar pressure waves occur sooner and lower. Thus there is a phase during which the lumbar pressure exceeds the cisternal, followed by one in which the cisternal exceeds the lumbar. These phenomena may be conveniently displayed on a differential trace. The phase during which the cisternal pressure exceeds the lumbar may be protracted. It is suggested that Froin's syndrome, central subarachnoid pouches and syringobulbia may be associated with upward pressure waves. Cough headache, the filling stages of communicating syringomyelia and tonsillar herniation may be associated with valve-like blockage at the foramen magnum which produces craniospinal pressure dissociation by interfering with downward or rebound pulsation. Decompensation of hydrocephalus after birth may be related to pulsation in association with crying; also after removal of a meningocele sac decompensation may be related to the effects of similar pulsation modified by changes in capacitance following operation. The cord destruction of syringomyelia, and the mechanisms which fill spinal subarachnoid cysts may be related to pressure waves directed both upwards and downwards. The merits and limitations of cough impulse as a clinical test for spinal blockage are discussed, and the suggestion is made that after further evaluation they may provide a more sensitive indication of spinal blockage than Queckenstedt's test.