  The DIRAC experiment at CERN has achieved a sizeable production of
$\pi^+\pi^-$ atoms and has significantly improved the precision on its lifetime
determination. From a sample of 21227 atomic pairs, a 4% measurement of the
S-wave $\pi\pi$ scattering length difference $|a_0-a_2| =
(.0.2533^{+0.0080}_{-0.0078}|_\mathrm{stat}.{}^{+0.0078}_{-0.0073}|_\mathrm{syst})M_{\pi^+}^{-1}$
has been attained, providing an important test of Chiral Perturbation Theory.
