  A combined analysis of Cosmic Microwave Background (CMB) and Lyman-a forest
data allows to constrain the matter power spectrum from small scales of about 1
Mpc/h all the way to the horizon scale. The long lever arm and complementarity
provided by such an analysis has previously led to a significant tightening of
the constraints on the shape and the amplitude of the power spectrum of
primordial density fluctuations. We present here a combined analysis of the
WMAP three year results with Lyman-a forest data. The amplitude of the matter
power spectrum sigma_8 and the spectral index ns inferred from the joint
analysis with high resolution Lyman-a forest data and low resolution Lyman-a
forest data as analyzed by Viel & Haehnelt (2006) are consistent with the new
WMAP results to within 1 sigma. The joint analysis with the mainly low
resolution data as analysed by McDonald et al. (2005) suggests a value of
sigma_8 which is ~ 2 sigma higher than that inferred from the WMAP three year
data alone. The joint analysis of the three year WMAP and the Lyman-a forest
data also does not favour a running of the spectral index. The best fit values
for a combined analysis of the three year WMAP data, other CMB data, 2dF and
the Lyman-a forest data are (sigma_8, ns) = (0.78\pm 0.03,0.96 \pm 0.01).
