The Spiegelberg device is based on air-filled balloon system and was designed for epidural ICP monitoring. Zero adjustment is done automatically with the device in situ, thus avoiding zero drift. In 14 patients with mostly severe head injury (Glasgow Coma Scale score of 8 or lower in 10 patients) and 19-84 years old monitoring was carried out during treatment in the intensive care unit. ICP values were checked by repeating functional tests of the monitoring system, by serial cranial CT, and by a study of the clinical outcomes. Four patients died. There were no technical problems or infections. Clinically reliable data were obtained in 10 patients. The ICP shown was correlated with all other parameters; it was lower than would be expected in 1, and higher in 3 patients. With six simultaneous measurements with Gaeltec ICT/b, Camino subdural or an intraventricular catheter system the values were found to correlate only in 1 case. Experimental and clinical data suggest that the Spiegelberg-monitored ICP is somewhat higher than the ICP shown by other epidural systems. Clinical trials will be continued.