  We review two manifestations of chiral symmetry breaking in the pion sector.
First, we examine the $\pi\pi$ scattering amplitude at threshold, which is
completely determined by the chiral symmetry breaking part of the strong
interaction, and, thus, directly constrains the form of the low energy
effective lagrangians. We review the current status of the $\pi\pi$ scattering
lengths in view of the recent results on reactions $\pi N \to\pi\pi N$ near
threshold, and discuss the needed improvements. Second, we focus on the rate of
the pion beta decay, determined at the tree level by the CVC hypothesis, a
remnant of chiral symmetry breaking. Precise knowledge of the $\pi\beta$ decay
rate constrains CKM unitarity, and, thus, can be used to distinguish among
certain extensions of the minimal Standard Model. Present status of CKM
unitarity, and the PIBETA experiment at PSI are discussed.
