All complications in a consecutive series of 648 patients subjected to prolonged recording of the ventricular fluid pressure (VFP) during 1982-1986 were registered and analysed. The procedure did not cause permanent symptoms or deficits in any case except for one haemorrhagic complication. Definite infections caused by the VFP recording were found in 4.3% of the 540 patients (83%) surviving their disease or lesion, and in 1.9% in non-survivors. These infections were almost exclusively registered in patients treated with prolonged drainage of hemorrhagic ventricular fluid, while definite infections in other patients were found in only 1.3%. Most infections were caused by Staphylococcus epidermidis and all infections could be treated successfully. Infection did not cause or contribute to the lethal outcome in any case. In 60% of the cases with infectious complications laboratory signs of ventriculitis occurred after a surgical revision of the ventriculostomy. The duration of VFP recording was of subordinate importance for the development of infection. In 13 patients (1.9%) during the studied period a reliable VFP recording was not obtained, a fact that points to the need for alternative methods in a minority of patients with elevated intracranial pressure. It is concluded that complications caused by VFP recording can be kept at an acceptably low frequency in patients without haemorrhagic cerebrospinal fluid demanding long-term drainage.