  We present measurements of Underlying Event observables in pp collisions at
$\sqrt{s}$ = 0.9 and 7 TeV. The analysis is performed as a function of the
highest charged-particle transverse momentum $p_{\rm T, LT}$ in the event.
Different regions are defined with respect to the azimuthal direction of the
leading (highest transverse momentum) track: Toward, Transverse and Away. The
Toward and Away regions collect the fragmentation products of the hardest
partonic interaction. The Transverse region is expected to be most sensitive to
the Underlying Event activity. The study is performed with charged particles
above three different $p_{\rm T}$ thresholds: 0.15, 0.5 and 1.0 GeV/$c$. In the
Transverse region we observe an increase in the multiplicity of a factor 2-3
between the lower and higher collision energies, depending on the track $p){\rm
T}$ threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and
Phojet. On average, all models considered underestimate the multiplicity and
summed $p_{\rm T}$ in the Transverse region by about 10-30%.
