Lithium abundances in halo subgiants

We present lithium abundances for 28 halo subgiants based on high resolution, high signal-to-noise ratio spectra. Excluding the known lithium-rich subgiant BD +23 3912, the maximum abundances are log epsilon(Li) = 2.35. While subgiants evolve from stars hotter than the main sequence turn-off with shallower convection zones that may have depleted lithium to a lesser degree, lithium abundances in halo subgiants are not in agreement with the primordial value as predicted from standard big bang nucleosynthesis combined with recent results from WMAP.