One ml of cerebrospinal fluid (CSF) from each patient with West syndrome and patients from disease control groups were analyzed separately by highly sensitive thin-layer chromatography/enzyme-immunostaining method. The levels (mean +/- S.D.) of GM1, GD1a, sum of GD1b, GT1b, and GQ1b, and total gangliotetraose-series gangliosides in West syndrome patients (n = 14) and in an age-matched control group (n = 14) were as follows: 11.6 +/- 7.8 and 30.9 +/- 12.3 ng/ml CSF, 51.5 +/- 23.2 and 91.7 +/- 41.2 ng/ml CSF, 129.6 +/- 57.6 and 195.9 +/- 123.6 ng/ml CSF, and 192.7 +/- 78.6 and 318.4 +/- 131.6 ng/ml CSF, respectively. The differences were statistically significant except for the sum of GD1b, GT1b, and GQ1b (by 2 sample t test). Because they are abundant in the outer surface of neuronal plasma membranes, gangliosides may play an important role in the transformation of a neuroblast into a functionally mature neuron. Low levels of CSF gangliotetraose-series gangliosides, especially GM1 and GD1a, in patients with West syndrome may suggest a maturation disturbance of the brain from an early developmental stage.