By means of cerebrospinal fluid (CSF) scintigraphy with 111In-DTPA injected following lumbar puncture in 18 patients after meningitis (12), with traumatic head injury (4), cholesteatoma (1) or a communicating hydrocephalus (1) the hypothesis of whether slow movement of CSF may contribute to the elevation of CSF protein and albumin content in neurological diseases other than spinal block was tested. The ratios of the count rates over the head (geometric mean of anterior and posterior view) at 23-25 h to 4-6 h after 111In-DTPA application (C24 h/C5 h) and the ratio 47-49 h to 23-25 h after injection (C48 h/24 h) were taken as measures of the velocity of 111In-DTPA disappearance from CSF. Both the CSF protein content and the CSF-to-serum albumin ratio correlated with C24 h/C5 h and C48 h/C24 h. Assuming log-linear elimination between 24 and 48 h the elimination half-life of 111In-DTPA was estimated to be 12.4-131.1 h (median = 31.7 h). It was concluded that slow CSF kinetics probably are involved in the elevation of CSF protein content in several neurological diseases.