  And IV is a low-surface brightness (LSB) dwarf galaxy at the distance of 6.1
Mpc, projecting close to M 31. In this paper the results of spectroscopy of And
IV the two brightest HII regions with the SAO 6-m telescope (BTA) are
presented. In both of them the faint line [OIII]4363 was detected that allowed
us to determine their O/H by the classical T_e method. Their values of
12+log(O/H) are equal to 7.49+-0.06 and 7.55+-0.23, respectively. The
comparison of these direct O/H determinations with the two most reliable
semi-empirical and empirical methods shows their good consistency. For And IV
absolute blue magnitude of M_B=-12.6, our value of O/H corresponds well to the
`standard' relation between O/H and L_B for dwarf irregular galaxies (DIGs).
And IV appears to be a new representative of the extremely metal-deficient
gas-rich galaxies in the Local Volume. The very large range of M(HI) for LSB
galaxies with close metallicities and luminosities indicates that the simple
models of LSBG chemical evolution are too limited to predict such striking
diversity.
