  Results are reported from a search for the effects of contact interactions
using events with a high-mass, oppositely charged muon pair. The events are
collected in proton-proton collisions at sqrt(s) = 7 TeV using the Compact Muon
Solenoid detector at the Large Hadron Collider. The data sample corresponds to
an integrated luminosity of 5.3 inverse femtobarns. The observed dimuon mass
spectrum is consistent with that expected from the standard model. The data are
interpreted in the context of a quark- and muon-compositeness model with a
left-handed isoscalar current and an energy scale parameter Lambda. The 95%
confidence level lower limit on Lambda is 9.5 TeV under the assumption of
destructive interference between the standard model and contact-interaction
amplitudes. For constructive interference, the limit is 13.1 TeV. These limits
are comparable to the most stringent ones reported to date.
