Expression of ganglioside markers GD3, GD2, and A2B5 was investigated in primary cell cultures isolated from fetal human brains of 12-15 weeks' gestation by immunocytochemistry. None of neuron-specific enolase (NSE)+ neurons expressed GD3, while large numbers of NSE+ neurons expressed GD2 (72%) or A2B5 (48%). In GFAP+ astrocytes, GD3 was expressed in a small population (3%) with a high proliferative capacity. GD2 expression was observed in 20% of GFAP+ astrocytes, while A2B5 was identified in a very small number (2%) of GFAP+ astrocytes. GD2 was coexpressed in a small population (11%) of GD3+ astrocytes, while A2B5 was colocalized in more than 50% of GD3+ astrocytes. In galactocerebroside+ oligodendrocytes, GD3 expression was not observed but a small population (8-9%) expressed GD2 and A2B5. In Ricinus communis agglutinin (RCA)+ microglia, neither GD3, GD2, nor A2B5 were identified. Our results indicate that in fetal human brain cell cultures, GD3 is expressed in a small population of astrocytes, while both GD2 and A2B5 are expressed in a large population of neurons and smaller populations of astrocytes and oligodendrocytes. Our results suggest that both GD3 and A2B5, cell type-specific markers for oligodendrocyte-type 2 astrocyte progenitor cells in the rat central nervous system, could not be utilized as valid markers for glial precursor cells in fetal human brain cell cultures.