  The early physics program at the ATLAS experiment includes measuring the
basic properties of proton proton collisions, such as charged particle
multiplicities, in order to constrain phenomenological models of soft
interactions in the LHC energy regime. An inclusive and well understood trigger
is crucial to minimize any possible bias in the event selection. The ATLAS
experiment uses two complementary types of minimum bias triggers. A
scintillator trigger sensitive to the forward regions of 2.1<|eta|<3.8 has been
proven to efficiently select proton proton collisions, while a trigger based on
counting hits in the inner tracking detector has provided a useful control
sample. The performance and efficiency measurements of these triggers and
detectors will be presented.
