  We characterize the binary population in the young and nearby OB association
Scorpius OB2 using available observations of visual, spectroscopic, and
astrometric binaries with intermediate-mass primaries. We take into account
observational biases by comparing the observations with simulated observations
of model associations. The available data indicate a large binary fraction (>
70% with 3sigma confidence), with a large probability that all intermediate
mass stars in Sco OB2 are part of a binary system. The binary systems have a
mass ratio distribution of the form f(q) ~ q^-0.4. Sco OB2 has a semi-major
axis distribution of the form f(log a) ~ constant (Opik's law), in the range
5-5e6 Rsun. The log-normal period distribution of Duquennoy & Mayor results in
too few spectroscopic binaries, even if the model binary fraction is 100%. Sco
OB2 is a young association with a low stellar density; its current population
is expected to be very similar to the primordial population. The fact that
practically all stars in Sco OB2 are part of a binary (or multiple) system
demonstrates that multiplicity is a fundamental factor in the star formation
process, at least for intermediate mass stars.
