The neuronal ceroid-lipofuscinoses (NCLs) are a group of recessively inherited neurodegenerative lysosomal storage diseases, the pathogenesis of which is unknown. In the present study, we have measured iron and cooper in cerebrospinal fluids (CSF) using methods that detect these metals in a "loosely bound" form, complexable to the chelators bleomycin and 1,10-phenanthroline. We studied 25 children with NCL, 21 children with encephalopathy of some other type, and 5 control children without neurological complications. The CSF concentrations of loosely bound iron at neutral pH values and of loosely bound copper did not correlate with the clinical diagnosis of the patients, nor did they parallel degenerative symptoms in NCL, such as mental impairment, visual loss, motor handicap, and epilepsy. However, the concentrations of loosely bound iron and copper increased significantly with the age of the patient; this is a novel finding and may represent increasing tissue destruction with age. Our present findings do not support a major role for primary iron toxicity in the development of neuronal degeneration. To investigate any secondary pathological role for malplaced transition metals, further research is required.