Aims: To determine the existence of undifferentiated neural crest cells in the spinal ganglia during early human development, and analyse spatial and temporal distribution of neurons and their subtypes, appearance of glial cells and their potential to divide. Methods: Immunohistochemical and immunofluorescence techniques were performed on tissues of 10 human conceptuses between 5th and 10th gestational weeks, using paraffin sections. Primary antibodies to phox2b, PGP9.5, S100, GFAP, IB4 and NF200 proteins were visualised using DAB or fluorescent secondary antibodies (Texas Red and Fluoresceinisothiocianate). T-test and Mann-Whitney test were used for statistical analysis. Results: All investigated proteins were present in the spinal ganglia between the 5th and 10th week of gestation. Nestin and phox2b were strongly expressed in the 5th and 6th developmental week (62% and 73%, respectively), slightly decreasing during the 7th and 8th week, and during the 9th and 10th week (56% and 59%, respectively). Dorsal parts of the spinal ganglia in comparison to ventral parts had a significantly higher rate of nestin- and phox2b-positive cells in the 7th and 8th week of gestation (Mann-Whitney, p=0,012 and p=0,007 respectively). Between the 5th and 10th week of development, the number of PGP9.5- positive cells was subsequently increasing from 41% to 55%, and was constantly higher in the ventral parts of ganglia. The number of NF200- and IB4-positive cells was lowest in the 5th and 6th developmental week (9% and 7% respectively). During the 7th and 8th week, number of NF200-positive cells doubled (18%), while the number of IB4-positive cells tripled (20%). Their number reached almost the same values (22% and 24%, respectively) during 9th and 10th week. During the whole investigated period, the number of NF200- and IB4-positive cells was higher in the ventral parts of ganglia. GFAP marker for supporting cells was two fold higher (21%) than S100 marker (11%) in 5th and 6th week. Their number nearly levelled in 7th and 8th week (23% and 28% respectively). In the 9th and 10th week, the level of GFAP reached 25%, while there were 40% of S100-positive cells. Between 5th and 10th week, the number of GFAP- and S100-positive cells was higher in ventral parts of ganglia. Colocalization of nestin and S100 with Ki-67 factor was observed during 5th to 10th week period, while PGP9.5 did not colocalize with Ki-67 or nestin. GFAP and S100 colocalized in majority of ganglion cells, while GFAP and nestin, as well as S100 and nestin, colocalized only in some cells. Conclusions: During the whole investigated period, markers for neural crest cells and neural and glial cells appeared simultaneously in the spinal ganglia. Undifferentiated cells proliferated and served as a pool of multipotent cells that could differentiate into different cell subtypes. While neurons did not divide, glial cells proliferated and their number significantly increased during the investigated period. Early existence of nociceptors and mechanoreceptors indicated possible appearance of pain and touch sensation. The expression of investigated proteins changed in a temporally and spatially restricted pattern, thus enabling differentiation of cell lines in the spinal ganglia. Changes in that pattern may lead to pathologic disturbances of spinal ganglia formation and function.