  We have analysed around 170 000 individual photometric WASP measurements of
15 well established lambda Bootis stars to search for variability. The lambda
Bootis stars are a small group of late-B to early-F, Pop. I, stars that show
moderate to extreme (surface) underabundances (up to a factor 100) of most
Fe-peak elements, but solar abundances of lighter elements (C, N, O and S).
They are excellent laboratories for the study of fundamental astrophysical
processes such as diffusion, meridional circulation, stellar winds, and
accretion in the presence of pulsation. From the 15 targets, eight are variable
and seven are apparently constant with upper limits between 0.8 and 3.0 mmag.
We present a detailed time series analysis and a comparison with previously
published results. From an asteroseismologic study we conclude that the found
chemical peculiarities are most probably restricted to the surface.
