  We examine a sample of 223 F, G and early K metal-poor subdwarfs ([m/H]<-1)
with high proper motions ($\mu > 0.2"/$ year) at the distances of up to 250 pc
from the Sun. By means of our own speckle interferometric observations
conducted on the 6 m BTA telescope of the Special Astrophysical Observatory of
the Russian Academy of Sciences, and the spectroscopic and visual data taken
from the literature, we determine the frequency of binary and multiple systems
in this sample. The ratio of single, binary, triple and quadruple systems among
221 primary components of the sample is 147:64:9:1. We show that the
distribution of orbital periods of binary and multiple subdwarfs is asymmetric
in the range of up to $P=10^{10}$ days, and has a maximum at $P=10^{2}-10^{3}$
days, what differs from the distribution, obtained for the thin disc G dwarfs
(Duquennoy & Mayor 1991). We estimated the number of undetected companions in
our sample. Comparing the frequency of binary subdwarfs in the field and in the
globular clusters, we show that the process of halo field star formation by the
means of destruction of globular clusters is very unlikely in our Galaxy. We
discuss the multiplicity of old metal-poor stars in nearby stellar streams.
