  Threshold expansions of the $\pi\pi$ and $K\overline{K}$ spin 0 and isospin 0
scattering amplitudes are performed. Scattering lengths, effective ranges and
so--called volume parameters are evaluated. Good agreement with the existing
experimental data for the $\pi\pi$ scalar--isoscalar amplitude is found. An
importance of future accurate measurements of the $K\overline{K}$ threshold
parameters is stressed. New data are needed to understand the basic features of
the scalar mesons.
