We present 3.6m ESO telescope spectroscopic observations of the system of the two blue compact dwarf galaxies SBS 0335–052 W and SBS 0335–052 E. The oxygen abundance in SBS 0335–052W is 12 + log O/H = 7.13 \pm 0.08 , confirming that this galaxy is the most metal-deficient emission-line galaxy known .
We find that the oxygen abundance in SBS 0335–052E varies from region to region in the range from 7.20 to 7.31 , suggesting the presence of an abundance gradient over a spatial scale of \la 1 kpc .
Signatures of early carbon-type Wolf-Rayet stars are detected in cluster # 3 of SBS 0335–052 E , corresponding to the emission of three to eighteen WC4 stars , depending on the adopted luminosity of a single WC4 star in the C iv \lambda 4658 emission line .