The correlation between the negative magnetoresistance and concentration of localized holes in Be/Si pair delta-doped GaAs structures grown by molecular beam epitaxy (MBE) was investigated. The negative magnetoresistance was observed in a high-temperature range. The magnitude of negative magnetoresistance is nearly proportional to the concentration of localized holes. The transition temperatures from the negative magneto resistance to the positive one decrease with increasing concentration of localized holes. The temperature dependence of the Hall mobility is similar to that of negative magnetoresistance for each sample. The Hall resistance was measured in order to investigate possible ferromagnetic ordering of localized spins at low temperatures. (c) 2007 Elsevier B.V. All rights reserved.